Cut the pork tenderloin into 1 1/2" thick slices.

Combine the flour, salt, pepper, onion powder, and garlic powder.

Dredge the medallions in the flour mixture and set aside.

Add 2 tablespoons of avocado oil into a large skillet over medium-high heat. Let it get nice and hot.

Brown the pork tenderloin medallions in batches on both sides. They don't need to be fully cooked, just nice and browned. Remove from the pan and set aside.

Melt 3 tablespoons of butter in the skillet. Add the mushrooms and turn the heat up a bit. Brown the mushrooms in the pan. Remove and set aside.

Melt the remaining tablespoon of butter and add the onions. Reduce the heat to medium and cook for 5-6 minutes, until they are tender and lightly browned. Add the garlic and cook for another minute.

Add the marsala or sherry to the pan and stir. Make sure to scrape up any fond (stuck on bits) and incorporate it into the sauce. Add the mushrooms back to the pan. Add the chicken or vegetable stock to the pan along with the browned pork medallions.

Let the pork simmer over medium-low heat in the pan for about 10-15 minutes. The sauce should be reduced by about half.

Stir in the cream and serve it all over mashed potatoes or pasta.