Preheat your oven to 350°F (175°C) and grease a 1½ quart baking dish.

Cook the pasta in a large pot of salted boiling water for 8-9 minutes until al dente. Drain and set aside.

Chop the turkey into small pieces and warm the mashed potatoes in the microwave.

In a mixing bowl, combine turkey, mashed potatoes, onion, celery, garlic, and half of the cheddar cheese. Season with salt and pepper.

Spread 3/4 cup of gravy across the bottom of the baking dish.

Stuff each pasta shell with the turkey and potato mixture and place them in the dish open-side up.

Sprinkle bread stuffing on top and drizzle with remaining gravy. Finish with the rest of the cheese.

Bake for 25-30 minutes until cheese is bubbly and golden brown. Let cool slightly before serving.