• 1 tbsp. unsalted butter
Season sirloin with 2 teaspoons salt and the sugar, cover and refrigerate overnight.
Remove sirloin from refrigerator and allow to come to room temperature before cooking, about 30 minutes.
Heat 2 tablespoons oil in large roasting pan over medium-high heat. Pat steak dry with paper towel, put meat in pan and cook for 3 to 4 minutes per side, or until browned, for medium rare. If you prefer your steak cooked past medium-rare, cook for an additional minute per side. Move the steak to a plate to rest.
In same pan over medium-high heat, add the 1 tablespoon oil. Add the mushrooms with a pinch of salt and cook, turning once, for 4 minutes, or until caramelized.