Sirloin in a Mushroom Sauce
with Caramelized Onion Mashed Potatoes & Roasted Carrots
- Milk
Our sirloin 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.
Ingredients
1 unit
Yellow Onion
1 clove
Garlic
12 ounce
Carrots
4 ounce
Button Mushrooms
16 ounce
Yukon Gold Potatoes
2 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
Cooking Oil
1 tablespoon
Butter
(Contains: Milk)
Salt
Pepper
1 teaspoon
Sugar
Nutrition Values
Utensils
Cooking Steps
• Adjust rack to top position and preheat oven to 425 degrees. Wash and dry produce. • Trim, peel, and cut carrots on a diagonal into 1-inch-thick pieces. Peel and dice potatoes into ½-inch pieces. (TIP: For speedier spud prep, skip the peeling.) Halve, peel, and thinly slice onion. Trim and thinly slice mushrooms. Peel and mince garlic.
• Toss carrots on a baking sheet with a large drizzle of oil, salt, and pepper. • Roast on top rack until browned and tender, 25-30 minutes. • Meanwhile, place potatoes in a medium pot with enough salted water to cover by 2 inches. Bring to a boil; cook until tender, 15-20 minutes. • Drain and return potatoes to pot. Mash with sour cream until smooth. Season with salt and pepper. • Keep covered off heat until ready to serve.
• While potatoes cook, heat a large drizzle of oil in a large, preferably nonstick, pan over medium-high heat. Add onion; cook, stirring occasionally, until browned and softened, 8-10 minutes. • Add 1 tsp sugar 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.
• 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 and cook to desired doneness, 3-6 minutes per side. • Transfer to a cutting board to rest.
• Add 1 TBSP butter and mushrooms to pan used for steak over medium-high heat. Cook, stirring, until softened, 3-5 minutes. • Add garlic; cook until fragrant, 30 seconds. • Stir in demi-glace and ¼ cup water (1⁄3 cup for 4 servings). Bring to a boil, then reduce to a low simmer. • Stir in mustard. Simmer until thickened, 2-3 minutes. Season with salt and pepper.
• Slice steak against the grain. • Divide mashed potatoes, carrots, and steak between plates. Top mashed potatoes with caramelized onion. Top steak with mushroom sauce and serve.
Customer reviews
Review summary
Updated on Sep 2026- Flavor: The mushroom sauce and caramelized onions are the highlights — rich, savory, and deeply satisfying when the dish comes together. Some found the sauce too strong, too sweet, or off-putting from the demi-glace; others loved it, so taste as you go and adjust.
- Ease of prep: This meal has more steps than most and takes longer than the listed time — plan for extra prep time, especially for caramelizing the onions, which need at least 15–20 minutes to truly soften and sweeten.
- Suggestions: Cook the onions low and slow — the suggested 8–10 minutes is not enough to fully caramelize them. If you find the mustard flavor too prominent in the sauce, stir it in at the very end and simmer briefly. Some reviewers preferred adding the caramelized onions into the mushroom sauce rather than serving them separately on the potatoes. Add a splash of water to the mashed potatoes if they seem dry, and a little extra butter or cream helps if one sour cream packet isn't quite enough.
- Leftovers: The mushroom sauce was noted as less enjoyable the next day by at least one reviewer, though the rest of the meal held up well.
- Steak: Uneven steak thickness was a recurring challenge — thinner pieces overcook quickly, so sear them separately or pull them from the pan earlier for a better result.
Reviews from our home cooks
We are retired and I had gotten to be such a boring cook - so this was my first order, Sirloin in a Mushroom Sauce. It was fun making it and I loved that all the ingredients are right there already - it turned out so good and the steak was awesome and my husband loved it. I might have to do this one again should it come up on the menu. Yum Yum
AWESOME! Sirloins were large and even in size. Mushroom sauce was delicious. The parts of this meal really felt "Premium"
The cut of sirloin was nice and the demi glaze sauce was out-of-this-world delicious!! It paired nicely with the carrots and potatoes. Next time, I'd skip adding sour cream to the potatoes.
This meal was good. The mushroom sauce was on the sweet side. Also, can you really carmalize onions in ten minutes? Mine were very light in color. I just added them to the mushrooms because I didn't think they would look right on the potatoes. The carrots were great. I really need to roast carrots more often.
This meal was delicious. Loved it all but need to work on the carrots, they always seem to burn. Loved the caramel used onions on the mashed potatoes and the mushrooms.
This was fantastic. Apparently I'm not as fast as your "suggested" time to prep/cook but I was very impressed with the quality of the sirloin and the mushrooms. Everything was great and the family raved that this was their favorite meal. It was very good.
Wonderful flavors. Mushroom placed over Potatoes instead of Sirloin is better combination. Overall, excellent.
Delish...sirloin was surprisingly good...usually eat tenderloin but thought we should try the sirloin and it had great flavor especially the sauce!
Was so good! The mushroom sauce was beyond perfect and the onions went great with the potatoes 🤤
We caramelized the onions in sherry vinegar and added red wine in lieu of water to the mushrooms. Wonderful Sunday dinner.
