Preheat the oven to 400°F (200°C).
Prepare the filling by sautéing mushrooms and garlic in olive oil.
Add spinach to the mushroom mixture and stir until wilted.
In a large bowl, combine the sautéed mixture with ricotta, Parmesan, salt, pepper, and fresh herbs.
Make a pocket in the beef tenderloin by slicing it lengthwise, being careful not to cut all the way through.
Stuff the tenderloin with the filling and secure with kitchen twine.
Season the outside of the tenderloin with salt and pepper.
Sear the tenderloin in a hot skillet until browned on all sides.
Transfer the tenderloin to the preheated oven and roast for 25-30 minutes, or until desired doneness.
Remove the tenderloin from the oven and let it rest before slicing.
Serve with beef broth drizzled over the top.