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Cast Iron Filet Mignon with Mustard Cream Sauce & Mushrooms

Elevate your steak dinner with this Cast Iron Filet Mignon topped with Mustard Cream Sauce and sauteed Mushrooms. It’s an easy and elegant restaurant-quality meal that you can make right at home – sure to be a show stopper!

We love to serve this with my Cheesy Scalloped Potatoes and my Crispy Air Fryer Green Beans.

The Absolute Best Filet Mignon Recipe

There are nights when I want a comforting casserole and then there are nights when I want a meal that’s a little different. This Filet Mignon with Mustard and Mushrooms is equally as comforting but on a whole other level.

There’s something really special about a steak dinner. Sometimes I make it for just my husband and me as an easy “at-home date night” dinner. And other times I’ll make it when we are having company over. It’s honestly so simple but incredibly elegant and flavorful.

The filet mignon sears perfectly in the sizzling hot cast iron skillet. Then, it’s paired with mushrooms and a creamy mustard sauce that’s to die for. It tastes just like the type of sauce you would get at a restaurant. It’s garlicky, with hints of onion, creamy, and tangy from dijon and stone ground mustard.

five filet mignon steaks with mushrooms and mustard sauce

Why Use A Cast Iron Skillet?

I love using a cast iron skillet in the kitchen. A perfectly seasoned skillet is just as good (if not better) as a non-stick pan. Here are the benefits of using a cast iron skillet.

  • A seasoned cast iron skillet is naturally non-stick. There are no funky chemicals or materials used. The pan absorbs cooking oil from being seasoned and is a great non-stick surface.
  • The pan stays hot. The temperature doesn’t fluctuate much in a cast iron skillet. Plus, it heats evenly across the entire bottom of the pan.
  • You will use less oil. Because of the non-stick surface it develops, you’ll use less cooking oil when you’re using it.
five filet mignon steaks with mushrooms and mustard sauce

Recipe Ingredients

Here is the list of ingredients you need to make this steak dinner. The exact amounts for each ingredient are listed below in the recipe card.

  • Filet Mignon: Filet Mignon is a cut from the tenderloin. Coming from this part of the cow means that it’s extremely lean and tender which makes it perfect for fine dining at home!
  • Butter: Searing steak in butter creates incredible flavor. You could use olive oil or sunflower oil if you are trying to avoid using too much butter.
  • Salt & Pepper: Always season a steak before searing. A little salt and pepper go a long way with a cut of beef, trust me!
  • Garlic: Go for fresh garlic here! It’s going to add so much flavor to the filets.
  • Thyme: Fresh thyme is infused into the butter and creates the ultimate herb flavor for the steak. Another herb that you could dry is rosemary.

For the Mustard Cream Sauce:

  • Butter: I recommend using unsalted butter for sauces (and many cooking applications). This way you can control the salt level of the dish.
  • Shallots: Shallots provide a great base flavor for many sauces. You could also use onion if you’re in a pinch but I highly recommend using shallots.
  • Garlic: Again, use fresh garlic here! The dried spice products will not have the same flavor and may even make the sauce taste too bitter.
  • Dijon Mustard: Dijon Mustard is a little more tangy and spicy than regular mustard.
  • Stone Ground Mustard: Stone Ground Mustard is grainy and has more texture to it than smooth dijon mustard. You could use spicy mustard as a substitute if you need to because it’s also a bit grainy.
  • Fresh Thyme: Dried thyme will work, too, but fresh thyme definitely tastes the best.
  • Salt & Pepper

For the Sautéed Mushrooms:

  • Butter: You could also use olive oil or sunflower oil to cook the mushrooms.
  • Shitake Mushrooms: Shitake Mushrooms are flavorful and meaty and they are a great choice for this dish. You could also use oyster or cremini mushrooms.
  • Baby Bella Mushrooms: If you want to use large portabella mushrooms, you can just cut them up into smaller pieces or strips.
  • Salt & Pepper
cooked filet mignon in a cast iron skillet with mustard sauce and mushrooms

How to Make Cast Iron Filet Mignon

Here is how to make Filet Mignon with Mustard and Mushrooms. There are a few different parts to this recipe – sauteeing the mushrooms, making the sauce, and cooking steak. Let’s get started!

First, make the mushrooms. You will melt the butter in a cast iron skillet and then sauté them until they are soft and slightly browned. Then season with salt and pepper and set aside.

Next, make the mustard cream sauce. Start by cooking the shallots and garlic in the butter until they are soft and fragrant.

Add the mustard and cream to the sauce. Whisk in the dijon mustard, stone ground mustard, thyme, and heavy cream until it’s bubbly. When it’s done, set the sauce aside while you cook the steaks.

Finally, cook the filets. Start by making sure that the cast iron skillet is very hot. Then add the butter and the steaks. Next, add the thyme and garlic to the pan.

Baste the steaks with the melted butter. Basting the steaks means pouring the melted butter on top of the steaks while you sear both sides.

Transfer the steaks to the oven. Now move the skillet with the filets into a preheated oven. Cook them for as long as you need to reach the desired doneness. Remember to let the steaks rest for a few minutes before serving.

Once they are done, serve them with the sauce and mushrooms. And then pour the mustard cream sauce on top of the steaks and serve with the cooked mushrooms. You’re done!

cast iron skillet with filet mignon cuts that have been cooked with mushrooms

Tips for the Perfectly Seared Steak

Here are some helpful tips for when you’re making this filet mignon dinner.

  • Let the meat come to room temperature. Beef steaks cook much better once you “take the chill off”. It will take less time to cook them and they will come out perfect if you let them reach room temperature first.
  • Make sure the cast iron pan is very hot before searing the steaks. You want to get that sizzle as soon as you put the filets in the pan!
  • Always let your meat rest after cooking it. I recommend that you always wait to slice your steak after it’s cooked. The steaks need a few minutes for the juices and heat to redistribute throughout the steak.

How Long To Cook Filet Mignon?

The cooking time for steak depends on how you like it cooked. For this recipe, I recommend searing the steak for 2 minutes on each side and then finishing the cooking process in the oven. Here are the suggested cooking times:

  • For medium rare: Cook for 5-6 minutes and check for an internal temperature of 120-125F.
  • For medium: Cook for 7-8 minutes and check for an internal temperature of 130-140F.
  • For medium-well: Cook for 9-10 minutes and check for an internal temperature of 140-150F.
  • For well done: Cook for 11-12 minutes and check for an internal temperature of 160F.

Keep in mind that these cooking times will vary depending on how thick the steak is.

Serving Suggestions

I’ve got some great side dish ideas for Filet Mignon with Mustard and Mushrooms! Below are some of my favorites.

How to Store & Reheat Leftovers

You can easily store and reheat the leftovers of this steak dinner. I recommend storing any steaks whole (not sliced) if you can, for the best flavor. Also, if you can, store the sauce separately.

Store the leftovers in an airtight container in the fridge for up to 5 days. You can use a cast iron skillet to reheat the steak or even an air fryer. I don’t usually recommend reheating steak in the microwave because it will comprise the tender texture of the beef.

Then you can use a small pan on the stove to reheat the sauce. If it’s too thick you can use a little water to thin it out.

five filet mignon steaks with mushrooms and mustard sauce
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filet mignon with mustard and mushrooms on a plate with potato and green beans

Cast Iron Filet Mignon with Mustard Cream Sauce & Mushrooms

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  • Author: Krista
  • Prep Time: 30 minutes
  • Cook Time: 30 minutes
  • Total Time: 60 minutes
  • Yield: 4 1x
  • Category: Steak
  • Method: Stove & Oven
  • Cuisine: American
  • Diet: Gluten Free


Elevate your steak dinner with this Cast Iron Filet Mignon topped with Mustard Cream Sauce and sauteed Mushrooms. It’s an easy and elegant restaurant-quality meal that you can make right at home – sure to be a show stopper!


  • 4 (6oz. filet mignon steaks)
  • salt & pepper
  • 2 tablespoons butter, unsalted
  • 45 whole garlic cloves, peel removed
  • 56 sprigs of thyme

Mustard Cream Sauce:

  • 1 tablespoon butter, unsalted
  • 1/4 cup minced shallots
  • 1 garlic clove, minced
  • 1/2 cup heavy cream
  • 1 tablespoon dijon mustard
  • 1 tablespoon stone ground mustard
  • 1 teaspoons of fresh thyme
  • salt & pepper to taste
  • 12 tablespoons of water (optional to thin sauce out)

Sauteed Mushrooms:

  • 1 tablespoons butter, unsalted
  • 3 oz. shitake mushrooms, roughly sliced
  • 5 oz. baby bella mushrooms, roughly sliced or cut into quarters
  • 1/4 teaspoon salt
  • 1/8 teaspoon pepper


Sauteed Mushrooms:

  1. Heat a large cast iron skillet to medium-high heat. Add butter, shitake mushrooms and baby bella mushrooms and saute for 3-5 minutes, stirring occasionally. 
  2. After 5 minutes, season with salt and pepper (this keeps the mushrooms from browning too early). Stir and cook an additional 2-3 minutes or until mushrooms are slightly browned. Set aside.

Cast Iron Filet:

  1. Allow steaks to sit on the counter 30 minutes prior to cooking to “take the chill off.”
  2. Generously season both sides with salt and pepper.
  3. Preheat oven to 400°F.
  4. Heat a large cast iron skillet to high heat. Add butter to the pan and immediately add seasoned steaks. Sear for 2 minutes and flip. Then add garlic cloves and thyme to the cast iron, sear the other side for 2 minutes – spooning butter over the top of the steaks throughout.
  5. Transfer the skillet, uncovered, to the oven and cook steaks for 5-6 minutes for medium rare, 7-8 minutes for medium, 8-9 minutes for medium-well and 10-11 minutes for well. Cooking times are not exact, it will depend on the thickness of your steak. If your steak is thick it will be longer, if your steak is thin it will need less cook time. A good way to be sure is to use a meat thermometer –  120°F to 125°F is medium rare.
  6. Remove steaks from the oven and let rest for 5 minutes.

Mustard Cream Sauce:

  1. Heat a medium skillet to medium-high heat. Add butter, shallots and garlic. Saute for 2-3 minutes, until shallots are translucent. Season with salt and pepper. 
  2. Next, add heavy cream, dijon mustard, stone ground mustard and fresh thyme. Whisk together to combine and bring to a slow simmer for about 2-3 minutes. If the mixture is too thick, add 1-2 tablespoons of water to thin it out. Set aside.

Assemble Steaks:

  1. Once steak have rested, top with pan seared mushrooms and mustard cream sauce. Serve.


  • Serving Size: 1 filet + sauce
  • Calories: 654
  • Sugar: 2 g
  • Sodium: 351 mg
  • Fat: 53 g
  • Saturated Fat: 26 g
  • Carbohydrates: 7 g
  • Fiber: 1 g
  • Protein: 37 g
  • Cholesterol: 178 mg

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