Prep pork: Trim silver skin from the pork tenderloin and cut crosswise into 12 medallions. Press each medallion with the palm of your hand to flatten to a about 1/2-inch even thickness. Whisk the flour and all pork seasoning together in a shallow dish. Dredge each medallion in the mixture, shake off any excess, then transfer to a dry surface.
Cook pork: Melt the 2 tablespoons butter in 2 tablespoons olive oil in a large skillet over medium-high heat. Once hot, add HALF of the pork medallions in a single layer and cook for approximately 3 minutes per side. Pork is cooked through when internal temperature registers at 145˚F. Cooking time will also depend on the thickness of the medallions. Transfer pork to a plate, tent with foil and repeat with remaining pork.
Caramelize mushrooms: Melt 2 tablespoons butter with 1 tablespoon olive oil over medium heat. Increase temperature to medium-high and add half of the mushrooms. Give them a stir to evenly coat in the butter then arrange mushrooms in a single layer. Cook mushrooms for 3 minutes per side or until golden. Once evenly browned, season mushrooms lightly with freshly cracked salt and pepper and give them a stir. Remove mushrooms from skillet and repeat with remaining mushrooms; transfer all mushrooms to a plate.
Gravy: To the now empty skillet, melt 2 tablespoons butter. Add shallot and sauté over medium-high heat for 2-3 minutes to soften. Reduce heat to medium, add garlic and red pepper flakes and sauté for 30 seconds. Add flour and cook for 1 minute, scraping up the browned bits on the bottom of the pan. Reduce heat to low and slowly whisk in beef broth. Add soy sauce, Worcestershire, Dijon, beef bouillon, and all seasonings. Bring to a simmer until thickened.
Assemble: Nestle the pork medallions into the pan and spoon some gravy over top. Cook over medium for a few minutes to warm through. Taste and season with salt and/or pepper to taste. Garnish with fresh parsley if desired. Serve over mashed potatoes (recommended), rice or pasta.