Spread one slice of bread with a thin layer of cold gravy. Layer the sandwich with slices of turkey, stuffing, more gravy and cranberry dressing, to taste. Season with salt and pepper and top with chopped sage leaves. Spread a thick layer of cranberry dressing on the other slice of bread.
Butter each side of the sandwich on the outside, then toast on a preheated sandwich grill or in a cast iron skillet, pressing the firmly on each side golden brown.