Preheat the oven to 350°F (175°C).
Slice the mini buns in half and place the bottoms in a baking dish.
Spread mayonnaise on the bottom halves of the buns.
Layer turkey, stuffing (if using), cranberry sauce, and cheese over the buns.
Place the top halves of the buns back on.
Brush melted butter over the tops of the buns and sprinkle with garlic powder and parsley.
Cover with foil and bake for 10–12 minutes, until the cheese is melted and sandwiches are warmed through.
Serve warm with turkey gravy for dipping, if desired.