Pan-Seared Sirloin Steak with Mushroom Sauce, Caramelized Onion Mashed Potatoes and Roasted Carrots

This sirloin steak recipe is all about bold, meaty flavor paired with comforting sides. A rich mushroom pan sauce adds savory depth to the perfectly seared steak, while creamy mashed potatoes with caramelized onions and tender roasted carrots round out the meal. It’s a hearty, satisfying dinner that feels special but comes together easily.

The key to this dish is building layers of flavor: sear the steak to a beautiful crust, then use the same pan to cook mushrooms and create a luscious demi-glace sauce. Meanwhile, the potatoes are mashed with sour cream and caramelized onions for extra richness and the carrots roast until sweet and tender. Every component complements the next for a truly memorable plate.

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Ingredients

14 ounce Sirloin SteakView ingredient guideLike ingredientDislike ingredient

1 unit OnionView ingredient guideLike ingredientDislike ingredient

12 ounce CarrotView ingredient guideLike ingredientDislike ingredient

6 tablespoon Sour CreamView ingredient guideLike ingredientDislike ingredient

1 unit Beef Demi-GlaceView ingredient guideLike ingredientDislike ingredient

1 clove GarlicView ingredient guideLike ingredientDislike ingredient

16 ounce PotatoesView ingredient guideLike ingredientDislike ingredient

2 teaspoon Dijon MustardView ingredient guideLike ingredientDislike ingredient

4 ounce Button MushroomsView ingredient guideLike ingredientDislike ingredient

teaspoon (tsp) Black PepperView ingredient guideLike ingredientDislike ingredient

teaspoon (tsp) SaltView ingredient guideLike ingredientDislike ingredient

Instructions

1. Preheat oven to 425°F. Peel and cut carrots into ½-inch thick sticks. Toss with a drizzle of oil, salt and pepper. Spread on a baking sheet and roast for 20-25 minutes, until tender and lightly browned.
2. While carrots roast, peel and dice potatoes into 1-inch cubes. Place in a pot, cover with cold salted water and bring to a boil. Cook until fork-tender, about 15 minutes. Drain and return to pot.
3. Meanwhile, thinly slice the onion. Mince the garlic. Slice the mushrooms.
4. Heat a large skillet over medium-high heat. Pat the sirloin steak dry and season generously with salt and pepper. Sear for 4-5 minutes per side for medium-rare or until desired doneness. Transfer to a plate and tent with foil.
5. In the same skillet, reduce heat to medium. Add a drizzle of oil and the sliced onions. Cook, stirring occasionally, until deeply caramelized, about 10 minutes. Remove half the onions and set aside for the mashed potatoes.
6. Add the mushrooms and minced garlic to the skillet with the remaining onions. Cook until mushrooms are golden and tender, about 4 minutes.
7. Stir in the beef demi-glace and ½ cup water. Bring to a simmer, scraping up any browned bits. Cook until slightly thickened, about 2 minutes. Stir in the Dijon mustard. Season with salt and pepper to taste.
8. Add the reserved caramelized onions and sour cream to the drained potatoes. Mash until smooth and creamy. Season with salt and pepper.
9. Slice the rested steak against the grain. Serve with mashed potatoes, roasted carrots and spoon the mushroom sauce over the steak.

Recipe Tips

FAQ

Can I use a different cut of steak?

Yes, ribeye or strip steak work well, but adjust cooking time based on thickness.

What can I substitute for beef demi-glace?

You can use 1 cup of beef broth simmered until reduced by half or a store-bought beef base.

Can I make this dairy-free?

Use dairy-free sour cream and omit the butter; the mashed potatoes can be made with olive oil and non-dairy milk.