Preheat your oven to 400°F.
Season the beef tenderloin generously with salt and pepper.
Heat a skillet over medium-high heat and sear the beef on all sides until a golden-brown crust forms, about 2-3 minutes per side.
Remove the beef from the pan and set aside to rest.
Finely chop the white mushrooms and shallot.
In the same skillet, add the olive oil and then the chopped mushrooms, shallot, fresh thyme, and rosemary. Sauté over medium heat until the mixture becomes a dry, finely textured duxelles, about 4-5 minutes.
Adjust seasoning in the duxelles with a pinch of salt and pepper.
Spoon the warm mushroom duxelles evenly over the rested beef tenderloin.
Optionally, return the beef topped with duxelles to a preheated oven or under a broiler for 2-3 minutes to meld the flavors.
Slice the beef and serve immediately, enjoying the blend of tender meat and savory, herb-infused mushrooms.