Lay the steaks on a large piece of plastic wrap. Combine the mustard, garlic, bourbon, and Worcestershire sauce in a small bowl. Slather the mixture evenly all over the tenderloin. Bring the sides of the plastic wrap over the tenderloin and wrap tightly. Allow to sit at room temperature for 1 hour.
Unwrap the plastic wrap and generously season the tenderloin on all sides with the salt and ground black and green peppercorns. Use your hands to pat the peppercorns into the steak.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Arrange the steaks and you mushrooms directly on the grill grate and smoke for 1 hour.
Remove the steaks and mushrooms from the grill. Increase the grill temperature to 400 degrees F allow the grill to preheat for 10 to 15 minutes.
In a large saucepan, drizzle olive oil and simmer 6 cloves of minced garlic on medium to low heat for 15 minutes or until the garlic begins to lightly.
Return the steaks the grill and cook until the internal temperature is 130 degrees F on an instant-read meat thermometer, 20 to 30 minutes, depending on the thickness of the steak. Do not overcook.
Add the white wine and chicken stock to the saucepan with the garlic and bring to a simmer.
Slice the smoked mushrooms and add them to the sauce. Cook until soft, about 5-7 minutes.
Turn the heat down to low and stir in the heavy cream. Season to taste with salt and pepper. Remove from heat.
Transfer the steaks to a platter and cover with foil. Let rest for 10 minutes before removing the foil and carving into thin slices. Ladle the sauce directly on the steaks, or serve underneath the thinly sliced steaks with crostinis. Can be served warm or at room temperature. Enjoy!