Preheat oven to 400F degrees.

In a large skillet, over medium high heat, heat the olive oil and sauté the onions and garlic until translucent (about 2 minutes).

Add the shredded turkey and sauté with the onions and garlic for a minute. (You can also add whatever leftover vegetables you have, as well as some corn or olives!) Then, add the gravy and the parsley and cook until incorporated. Season with salt and pepper, if necessary. Reserve,

If your mashed potatoes have thickened too much in the fridge, add 1/2 cup heavy cream to loosen it up a bit.

Spread 1/4 of the mashed potatoes to the bottom of a lightly greased 9X13-inch baking dish. Layer the turkey filling right on top of that and finish with the remaining mashed potatoes on top.

Sprinkle the parmesan on top and bring the casserole to the oven. Bake for 30 minutes or until the top is bubbly and golden brown. Top with some more parmesan cheese, if desired!