Quarter mushrooms.

Peel and cut potatoes into large evenly-sized chunks.

Halve and peel onion. Slice halves into thin strips.

Pat steaks dry, and season both sides with 1/4 tsp. salt. Season one side with coarse black pepper.

Place mushrooms on one half of prepared baking sheet and toss with 2 tsp. olive oil and a pinch of salt and pepper.

Add onion to empty half and toss with 2 tsp. olive oil and a pinch of salt.

Spread mushrooms and onion into even layers on their sides (some overlap is OK). Roast in hot oven until vegetables are browned and softened, 20-25 minutes.

While mushrooms and onion roast, make mashed potatoes.

Bring a medium pot with potatoes covered by lightly salted water to a boil. Once boiling, cook until tender, 14-18 minutes.

Reserve 1/2 cup potato cooking water. Drain potatoes in a colander and return to pot.

Add sour cream and 1/4 tsp. salt and mash until smooth. If too dry, add reserved potato cooking water, 1 Tbsp. at a time, until desired consistency is reached. Cover and set aside.

While potatoes boil, cook steaks.

Place a medium non-stick pan over medium heat and add 2 tsp. olive oil.

Add steaks to hot pan, peppered-side down first. Cook until browned, pepper is aromatic, and steaks reach desired doneness, or 4-6 minutes per side for medium/medium-well. Steak thickness can vary; if you receive a thinner steak, we recommend checking for doneness sooner.

Remove steaks to a plate and tent with foil. Wipe pan clean and reserve.

Return pan used to cook steaks to medium-high heat. Add demi-glace and 1/4 cup water to hot pan. Stir to combine, then bring to a boil.

Once boiling, cook until thickened slightly, 1-2 minutes.

Remove from burner and stir in butter until combined.

Plate dish as pictured on front of card, placing steak on sauce and topping mashed potatoes with roasted onions. Bon appétit!