Begin by drying the filet mignon with paper towels to ensure a good sear. Generously season both sides with kosher salt and black pepper, then let the steaks rest at room temperature for 30 to 60 minutes.

While the steaks rest, slice the baby bella mushrooms and mince the garlic cloves. Combine the all-purpose flour, garlic powder, and onion powder in a bowl.

Heat a large skillet over medium-high heat and add the unsalted butter and olive oil. Once melted, coat each steak with the flour mixture and place them in the skillet. Sear for 2 to 3 minutes on each side.

Remove the steaks from the skillet and cover with aluminum foil to keep warm. Let rest for at least 5 minutes.

In the same skillet, add the sliced mushrooms over medium heat and cook for about 5 minutes until softened. Add the minced garlic and fresh thyme, cooking for an additional minute.

Pour the marsala wine into the skillet and scrape any brown bits from the bottom. Bring to a simmer and reduce for about 3 to 4 minutes.

Stir in the beef stock and let simmer for another 2 to 3 minutes. Lower the heat and gently mix in the heavy cream, warming through and becoming luxurious.

Return the seared steaks to the skillet, spooning the creamy sauce over them for an additional 3 to 5 minutes.

To serve, place each steak on a serving dish and generously spoon the creamy marsala sauce with mushrooms over the steak.