Gather all ingredients and equipment. Preheat oven to 400 degrees. In a medium-sized bowl, add mashed potatoes, sour cream, mozzarella, cheddar, bacon, green onions; mix until fully combined and evenly distributed.
Crack an egg and place in a bowl and whisk together to use as an egg wash; set aside.
Unbox pizza dough, unroll, and spread on a clean surface. On one half of the dough, spread filling evenly. Then fold over other half of dough and tightly crimp edges together. The shape should be a half-circle. Place on a parchment paper-lined baking sheet. Cut air vents then brush egg wash over calzone.
Place in a 400-degree oven for 15 minutes or until golden brown. Remove from oven and slightly cool; serve.