Flat Iron Steak with Mushroom Sauce

Preheat the oven to 325 degrees F (165 degrees C).

Season both sides flat iron steak with salt, black pepper, garlic powder, and onion powder. Heat a heavy, oven-proof skillet over medium-high heat; add 2 teaspoons vegetable oil and heat until oil shimmers. Add steak; sear until well browned, about 3 minutes per side. Remove steak from skillet and reduce heat to medium.

Add remaining 1 teaspoon vegetable oil to skillet. Add mushrooms; cook and stir until wilted and browned, about 10 minutes. Reduce heat to medium-low; add wine to skillet and bring to a boil. Cook until wine is slightly reduced, 3 to 5 minutes; add beef stock and bring to a simmer.

Mash butter and flour into a paste in a small bowl, using a fork; stir into mushroom mixture and simmer until sauce is thickened, about 5 minutes. Return flat iron steak to the skillet.

Cook in the preheated oven until steak is barely pink inside, about 10 minutes. Cut steak into thin slices on the diagonal; place on a platter.

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