To make filling: In a medium size pot, cover potatoes completely with cold water. Add ½ teaspoon salt and bring to a boil. Lower heat to medium-high cooking for 8-10 minutes or just until fork tender. Drain well.
To the potatoes, add butter, cream cheese, reserved ½ teaspoon salt, granulated garlic and black pepper to taste. Whip with an electric mixer until smooth. (You may adjust salt to taste.)
Mix in shredded cheese, bacon and green onion by hand. Chill potato filling for 1-2 hours or overnight. (Reserve 2 tablespoon green onion for garnishing)
To assemble: Brush wonton wrappers with beaten egg on all outside edges. Fill wonton wrappers with about 1 tablespoon potato filling. Roll up starting with pointed edge, folding sides into filling ending pointed edge side down. Seal adding a bit with more egg, if needed to seal.
Preheat 2 inches of oil in a deep skillet or pot and heat to 350-360°F. Fry spring rolls in batches for 3-4 minutes, until crispy and golden, turning for even browning. Have nearby a pan lined with paper towels. Remove from oil using a slotted spoon to pan to drain.
Serve immediately garnished with reserved bacon and onion with sour cream or ranch dressing for dipping.