Preheat the oven to 375°F (190°C).

Prepare the stuffing. In a skillet, sauté garlic, mushrooms, and spinach until soft.

Combine the sautéed mixture with stuffing mix, parmesan cheese, thyme, and broth. Stir until mixed well.

Season the beef tenderloin with salt and pepper on all sides.

Using a sharp knife, carefully cut a pocket in the center of the beef tenderloin.

Stuff the beef tenderloin with the prepared stuffing mixture, pressing it tightly.

For additional flavor, wrap the stuffed tenderloin with bacon strips, securing with kitchen twine if needed.

Place the stuffed tenderloin in a roasting pan and roast for about 50-60 minutes, or until the internal temperature reaches 135°F (57°C).

Remove from oven and let the beef rest for 10-15 minutes before slicing.

Slice into thick pieces and serve immediately, garnished with fresh herbs if desired.