Peel if desired or leave on the red skins. Cube into bite size pieces and layer into a 9 x 13" pan
Cube the cheese and put in a bowl add the mayo and stir until combined. Spread over potatoes and cover completely. If you need to add more cheese or mayo do so. Optional sprinkle with finely chopped green onions.
Bake at 350 degrees for 30-40 minutes until cheese is brown and bubbly.