Crack the egg into a large mixing bowl and whisk until frothy.
Add in the mashed potatoes, bacon, both cheeses, ½ cup of the flour, green onions, and seasonings to taste. Stir the mixture together until well combined.
Pour the other ½ cup of flour into a shallow bowl.
Divide the mashed potato mixture into 12 portions. Roll each piece into a ball and then flatten into a pancake.
Dredge each pancake lightly in the extra flour.
Heat the butter in a large skillet over medium heat.
Fry the pancakes in batches for about 2-3 minutes per side, until golden brown.
Serve immediately with sour cream if desired.
NOTE ON MASHED POTATOES: Taste your cold mashed potatoes again before making this recipe. Feel free to add extra salt, pepper, garlic, onion powder, smoked paprika, or herbs to your own personal taste.