Sirloin in a Mushroom Sauce
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Sirloin in a Mushroom Sauce

Sirloin in a Mushroom Sauce

with Caramelized Onion Mashed Potatoes and Roasted Carrots

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.

Family Friendly

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

Total Time50 minutes
Prep Time


serving amount

1 unit

Yellow Onion

2 clove


12 ounce


4 ounce

Button Mushrooms

16 ounce

Yukon Gold Potatoes

6 tablespoon

Sour Cream

(Contains Milk)

14 ounce

Sirloin Steak

1 unit

Beef Demi-Glace

(Contains Milk)

2 teaspoon

Dijon Mustard

Not included in your delivery

2 tablespoon

Vegetable Oil

3 tablespoon


(Contains Milk)



1 teaspoon



Nutrition Values

/ per serving
Energy (kJ)4017 kJ
Calories960 kcal
Fat52 g
Saturated Fat25 g
Carbohydrate73 g
Sugar22 g
Dietary Fiber12 g
Protein41 g
Cholesterol205 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.


Baking Sheet
Medium Pot
Small Bowl
Medium Pan
Paper Towel
Potato Masher



Adjust rack to top position and preheat oven to 425 degrees. Wash and dry all produce. Halve, peel, and thinly slice onion. Mince garlic. Peel and cut carrots on a diagonal 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.

Roast Carrots and Boil Potatoes

Toss carrots on a baking sheet with a large drizzle of oil, salt, and pepper. Roast on top rack, flipping halfway through, until tender, 25-30 minutes. Meanwhile, place potatoes in a medium pot with enough salted water to cover by 2 inches. Boil until tender, 15-20 minutes. Drain well; return potatoes to pot.

Caramelize Onion

Meanwhile, heat a large drizzle of oil in a medium, preferably nonstick, pan over medium-high heat. Add onion; cook, stirring occasionally, until browned and softened, 8-10 minutes. Add 1 tsp sugar (2 tsp for 4) and a splash of water; cook until caramelized, 2-3 minutes more. Season with salt and pepper. Turn off heat; transfer to a small bowl. Wipe out pan.

Mash Potatoes and Cook Steak

Meanwhile, heat pot with potatoes over low heat. Mash with sour cream, salt, and pepper until smooth. Keep covered until ready to serve. Pat steak dry with paper towels; season all over with salt and pepper. Heat a large drizzle of oil in pan used for onion over medium-high heat. Add steak; cook until browned, 3-6 minutes per side. Transfer steak to a second baking sheet. Roast until cooked to desired doneness, 4-7 minutes. Set aside to rest.

Make Sauce

Melt 2 TBSP butter (3 TBSP for 4 servings) in pan used for steak over medium-high heat. Add mushrooms and cook, stirring, until softened, 2-4 minutes. Add garlic and cook until fragrant, 30 seconds to 1 minute. Stir in demi-glace and ¼ cup water (⅓ cup for 4). Bring to a boil, then reduce to a low simmer. Stir in mustard. Simmer until slightly thickened, 3-4 minutes. Turn off heat; stir in 1 TBSP butter until melted.


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