Begin by seasoning the filet mignon generously with kosher salt and freshly ground black pepper on all sides. Let the steaks rest at room temperature for about 30 minutes.

While the steak is resting, slice the baby bella mushrooms and mince the garlic cloves. In a separate bowl, combine the all-purpose flour, garlic powder, and onion powder.

In a large skillet, heat the olive oil and unsalted butter over medium-high heat until the butter is melted and bubbly. Carefully dredge each steak in the flour mixture and place them in the hot skillet. Sear the steaks for 2-3 minutes on each side until they form a rich golden-brown crust.

In the same skillet, add the sliced mushrooms and sauté for about 5 minutes until they are tender and golden brown. Next, add the minced garlic and fresh thyme stems, cooking for another minute.

Pour in the marsala wine, scraping the bottom of the skillet to lift any browned bits. Allow the mixture to simmer for about 2 minutes.

Stir in the beef stock, allowing it to simmer for 3-4 minutes. As the sauce thickens slightly, lower the heat and incorporate the heavy cream, mixing until well blended.

Return the seared steaks to the skillet, spooning the creamy sauce over the top. Let them simmer gently for an additional 3-5 minutes.

To serve, place each filet mignon on a plate whole or slice it for an elegant presentation. Generously spoon the creamy sauce and mushrooms over the top.