stir and toss together the flour, potato starch, sugar (if used), baking powder, salt and tyme. Set aside. In a medium bowl whisk together the milk and mashed potatoes, then add the egg, melter butter (or margarine) and cheese, and whisk until well mixed. Add to the combined dry ingredients and stir just until blended. Spoon into the prepared muffin tins, filling each cup about 0.75 full. Bake until a toothpick inserted in the center of a muffin comes out clean, 15 to 18 minutes. Cool in the tins for 3 minutes, then remove.