Steak with Mushroom Sauce and Caramelized Onion Mashed Potatoes

This hearty dish features perfectly seared sirloin steak topped with a savory mushroom sauce. The creamy mashed potatoes are elevated with caramelized onions, while roasted carrots add a touch of sweetness.

Every element comes together for a satisfying meal that feels special enough for a celebration but simple enough for a weeknight. The rich demi-glace and Dijon mustard create a deeply flavorful sauce that complements the steak beautifully.

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Ingredients

2 unit Yellow OnionView ingredient guideLike ingredientDislike ingredient

4 clove GarlicView ingredient guideLike ingredientDislike ingredient

24 ounce CarrotsView ingredient guideLike ingredientDislike ingredient

8 ounce Button MushroomsView ingredient guideLike ingredientDislike ingredient

32 ounce Yukon Gold PotatoesView ingredient guideLike ingredientDislike ingredient

12 tablespoon Sour CreamView ingredient guideLike ingredientDislike ingredient

28 ounce Sirloin SteakView ingredient guideLike ingredientDislike ingredient

2 unit Beef Demi-GlaceView ingredient guideLike ingredientDislike ingredient

4 teaspoon Dijon MustardView ingredient guideLike ingredientDislike ingredient

2 tablespoon Vegetable OilView ingredient guideLike ingredientDislike ingredient

3 tablespoon ButterView ingredient guideLike ingredientDislike ingredient

SaltView ingredient guideLike ingredientDislike ingredient

PepperView ingredient guideLike ingredientDislike ingredient

Instructions

1. Adjust rack to upper position and preheat oven to 425°F. Wash and dry all produce. Halve, peel, and thinly slice onions. Mince garlic. Peel and cut carrots diagonally into 1-inch-thick pieces. Trim and thinly slice mushrooms. Peel and dice potatoes into ½-inch pieces. (For speedier prep, skip peeling the potatoes.)
2. Toss carrots on a baking sheet with a large drizzle of oil, salt, and pepper. Roast, flipping halfway through, until browned and tender, about 25 minutes. Meanwhile, place potatoes in a medium pot with enough salted water to cover by 2 inches. Boil until tender, about 15 minutes, then thoroughly drain.
3. Meanwhile, heat a large drizzle of oil in a medium pan over medium-high heat (use a nonstick pan if you have one). Add onions and cook, stirring occasionally, until browned and softened, about 15 minutes. Add a splash of water every now and then, scraping up any browned bits on bottom. Season with salt and pepper. Transfer to a small bowl.
4. Return drained potatoes to empty pot. Stir in sour cream, salt, and pepper. Mash over low heat until smooth. Keep covered until ready to serve. Pat steak dry with paper towels; season with salt and pepper. Wipe out pan used for onions, then heat a large drizzle of oil in it over medium-high heat. Add steak and cook to desired doneness, 3-6 minutes per side. Remove from pan and set aside to rest.
5. Add 2 tablespoons butter and mushrooms to same pan over medium-high heat. Cook, stirring, until softened, 2-4 minutes. Add garlic and cook until fragrant, about 1 minute. Stir in demi-glace and ⅓ cup water. Bring to a boil, then lower heat to a simmer. Stir in mustard. Simmer until slightly thickened, 3-4 minutes. Turn off heat; stir in 1 tablespoon butter until melted.
6. Slice steak against the grain. Divide potatoes, carrots, and steak between plates. Top potatoes with onions. Top steak with sauce, making sure to include mushrooms.

Recipe Tips

FAQ

Can I use a different cut of steak?

Yes, you can substitute with ribeye or strip steak, but adjust cooking time accordingly.

Can I make this dairy-free?

You can use dairy-free sour cream and butter alternatives, but the flavor and texture may vary.

How do I store leftovers?

Store components separately in airtight containers in the fridge for up to 3 days. Reheat gently.