4 (5 to 6-ounce) filet mignon steaks, about 1-inch thick
1 teaspoon salt, divided
1/2 teaspoon ground black pepper, divided
2 tablespoons olive oil, divided
2 tablespoons all-purpose flour
2 tablespoon unsalted butter, divided
10 ounces white mushrooms, sliced
1 medium red onion, thinly sliced
1/4 teaspoon dried thyme
5 garlic cloves, minced
2/3 cup dry marsala wine
1 1/2 cups unsalted chicken broth
1. Season the steaks with 1/2 teaspoon of the salt and 1/4 teaspoon of the pepper.
2. Heat 1 tablespoon of the oil in a large nonstick skillet over medium heat. Add the steaks and cook until they are well browned and an instant read thermometer inserted into the thickest part registers 115°F, about 4-5 minutes per side. Transfer the steaks to a plate and tent loosely with foil.
3. Dissolve the flour in 3 tablespoons of water and set the slurry aside.
4. Increase the heat to medium-high and add the remaining 1 tablespoon oil and 1 tablespoon of the butter. When the butter melts, add the mushrooms, onion, thyme, and the remaining 1/2 teaspoon salt and 1/4 teaspoon black pepper. Cook, stirring occasionally, until the vegetables are softened, about 5 minutes. Stir in the garlic and continue cooking until the mushrooms start to brown, another 3-4 minutes. Pour in the marsala, bring to a boil and cook until the liquid is nearly evaporated, about 2 minutes. Add the broth, bring to a boil, and cook until slightly reduced, about 3 minutes. Stir in the flour slurry and cook, stirring, until thickened, 1 minute. Return the steaks to the skillet and cook, turning occasionally, until the meat is heated through to an internal temperature is 130°F, about 3-4 minutes. Remove the skillet from the heat and swirl in the remaining 1 tablespoon of butter until melted.