---
title: 'Sirloin Steak "Diane" with Dijon-Mushroom Sauce'
servings: 4
source:
  name: HelloFresh
  url: https://www.hellofresh.com/recipes/sirloin-steak-diane-with-dijon-mushroom-sauce-698f602e753621b2c23a1759
prep time: 20 minutes
cook time: 30 minutes
time required: 50 minutes
difficulty: medium
allergens:
  - Milk
tags:
  - Protein Smart
rating: null
rating_count: null
source_chef: "Recipe Development Team"
review_highlights: []
nutrition:
  calories: 910
  protein: 42
  fat: 48
  saturated fat: 17
  carbohydrates: 76
  sugar: 20
  fiber: 9
  cholesterol: 155
  sodium: 790
  potassium: 2320
  calcium: 150
  iron: 4.6
image: "https://images.recipes.furrysalamander.com/Beef%20Recipes/Sirloin%20Steak/sirloin-steak-diane-with-dijon-mushroom-sauce.avif"
---
Adjust rack to top position and preheat oven to 425 degrees. Wash and dry produce. Trim, peel, and cut @carrot{24%ounce} on a diagonal into 1-inch-thick pieces. Peel and dice @potatoes{32%ounce} into ½-inch pieces. (TIP: For speedier spud prep, skip the peeling.) Halve, peel, and thinly slice @onion{1%unit}. Trim and thinly slice @button mushrooms{8%ounce}. Peel and mince @garlic{2%clove}.

Toss @carrot on a #baking sheet with a large drizzle of @cooking oil{2%tablespoon}, @salt{1%teaspoon}, and @black pepper{1%teaspoon}. Roast on top rack until browned and tender, ~{25%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%minutes}. Drain and return potatoes to pot. Mash potatoes with @sour cream{3%tablespoon} until smooth. Season with @salt and @black pepper. Keep covered off heat until ready to serve.

While potatoes cook, heat a large drizzle of oil in a #large pan{} over medium-high heat. Add @onion and cook, stirring occasionally, until browned and softened, ~{8%minutes}. Add @sugar{1%teaspoon} and a splash of @water{}; cook until caramelized, stirring occasionally, ~{2%minutes} more. Season with @salt and @black pepper. Turn off heat; transfer to a small bowl. Wipe out pan.

Pat @sirloin steak{24%ounce} dry with @paper towels{}; season with @salt and @black pepper. Heat a large drizzle of oil in same pan over medium-high heat. Add steak and cook to desired doneness, ~{5%minutes} per side. Transfer to a cutting board to rest.

Add @butter{1%tablespoon} (2 TBSP butter for 4 servings) and @button mushrooms to same pan over medium-high heat. Cook, stirring, until browned and softened, ~{3%minutes}. Add @garlic and cook, stirring, until fragrant, ~{30%seconds}. Stir in @beef demi-glace{2%unit} and @water{¼%cup}. Bring to a boil, then reduce to a simmer. Stir in @dijon mustard{4%teaspoon}. Simmer until thickened, ~{2%minutes}. Season with salt and pepper.

Slice steak against the grain. Divide @potatoes, @carrot, and steak between plates. Top potatoes with caramelized onion. Top steak with mushroom sauce and serve.