Revove neck and giblets from turkey and rinse bird. Dry, tuck back wings, and set aside.
Melt 7T. butter and cook onions till soft. Pour over mashed potatoes.
Add sage, 1T. salt, 1/2t. pepper, and 1/2 t. mustard to potatoes. Mix well.
Potatoes can be kept warm and served alongside bird OR you can line the inside cavity of the bird with cheesecloth (double it over for added strength) and cook stuffing in the cavity of the bird. Make sure to tie legs if doing so.
Mix 8T. softened butter with 2T. mustard, 1T. salt, 1/2 t. pepper, and 3T. flour and spread over breast and legs of turkey (the husband likes to double the plaster and spread over the entire bird. If doing so, it helps the plaster stick if you lightly dust the entire bird with flour first.).
Criss-cross bacon over breast if desired.
Bake until thermomter registers 160 degrees in breast and thigh (start checking at 3 hours).