Heat an oven proof pot, pan or skillet to medium high heat. Drizzle olive oil over the pork and rub the herbs de provence all over the tenderloin. Once the pan is hot, sear all sides, then put in the oven to finish cooking for about 20 minutes or until it reaches an internal temperature of 145-150F (will continue cooking while tented).
Remove from the pot and tent with foil. Allow to rest for 10 minutes, while you make the mushrooms.
In the same pot, heat to medium on the stove top and add in your butter, olive oil and mushrooms. Sauté until they have some good color, should take about 5 minutes or so.
Push the mushrooms to one side of the pan and add in the garlic. Sauté for about 20 seconds, careful not to burn. Deglaze the pan with white wine, scraping up the brown bits.
Add in the chicken stock and cook for another 5 minutes or until the liquid has reduced. Stir in the heavy cream and continue cooking while you slice the pork into medallions.
Serve the pork with the mushroom gravy over the top and enjoy!