Flat Iron Steak with Mushroom Sauce

Step 1
Preheat oven to 325 degrees F (165 degrees C).

Step 2
Sprinkle both sides of flat iron steak with salt, black pepper, garlic powder, and onion powder. Heat a heavy, oven-proof skillet over medium-high heat, pour 2 teaspoons vegetable oil into the hot skillet, and heat until oil shimmers. Sear steak in the hot oil until well browned, about 3 minutes per side. Remove steak from pan and reduce heat to medium.

Step 3
Pour 1 more teaspoon vegetable oil into skillet; cook and stir cremini mushrooms in hot oil until wilted and browned, about 10 minutes. Lower heat to medium-low; pour wine into mushrooms and bring to a boil. Cook until wine is slightly reduced, 3 to 5 minutes; add beef stock to vegetable mixture. Bring mixture to a simmer.

Step 4
Stir butter and flour into a paste in a small bowl, using a fork. Stir flour paste into mushroom mixture and simmer until sauce is thickened, about 5 minutes. Place flat iron steak into skillet with mushroom sauce.

Step 5
Place skillet in preheated oven and cook until steak is barely pink inside, about 10 minutes. Cut steak into thin slices on the diagonal and place meat on a platter.

Step 6
Stir cream into mushroom sauce until heated through, 1 to 2 minutes; pour over steak and garnish with chives.