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American Recipes
Sirloin in a Mushroom Sauce

Sirloin in a Mushroom Sauce

with Caramelized Onion Mashed Potatoes and Roasted Carrots

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Our New York strip steak has such a deep, rich, and gloriously meaty flavor that it could be a stand-alone dish with little more than salt and pepper for seasoning. But we’re still adding some top-notch sides and a full-bodied sauce to this recipe so that it soars above and beyond. Ultra-creamy mashed potatoes and tender roasted carrots make it filling and hearty, while the mushroom pan sauce that’s spooned on top has savory complexity.


Produced in a facility that processes milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and soybean.

Preparation Time50 minutes
Cooking difficultyLevel 1
serving amount
Ingredientsarrow down iconarrow down icon
serving amount

1 unit

Yellow Onion

2 clove


12 ounce


4 ounce

Button Mushrooms

16 ounce

Yukon Gold Potatoes

6 tablespoon

Sour Cream


14 ounce

Sirloin Steak

1 unit

Beef Demi-Glace


2 teaspoon

Dijon Mustard

Not included in your delivery

2 tablespoon

Vegetable Oil

2 tablespoon





Nutrition Values/ per serving
Nutrition Valuesarrow down iconarrow down icon
/ per serving
Energy (kJ)3766 kJ
Calories900 kcal
Fat64 g
Saturated Fat20 g
Carbohydrate72 g
Sugar19 g
Dietary Fiber12 g
Protein49 g
Cholesterol190 mg
Sodium860 mg
Due to the different suppliers we purchase our products from, nutritional facts per meal can vary from the website to what is received in the delivered box, depending on your region.
Utensilsarrow down iconarrow down icon
Baking Sheet
Medium Pot
Small Bowl
Medium Pan
Paper Towel
Potato Masher
Instructionsarrow up iconarrow up icon
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Adjust rack to upper position and preheat oven to 425 degrees. Wash and dry all produce. Halve, peel, and thinly slice onion. 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. (TIP: For speedier spud prep, skip the peeling.)

Cook Veggies
Cook Veggies

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.

Caramelize Onion
Caramelize Onion

Meanwhile, heat a large drizzle of oil in a medium pan over medium-high heat (use a nonstick pan if you have one). Add onion 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.

Mash Potatoes and Cook Steak
Mash Potatoes and Cook Steak

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 onion, 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.

Make Sauce
Make Sauce

Add 2 TBSP 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 ¼ cup water. Bring to a boil, then lower heat to a simmer. Stir in mustard. Simmer until slightly thickened, 1-2 minutes. Season with salt and pepper.

Plate and Serve
Plate and Serve

Slice steak against the grain. Divide potatoes, carrots, and steak between plates. Top potatoes with onion. Top steak with sauce, making sure to include mushrooms.