Place the potatoes in a pot of boiling water and cook until tender. Drain and place in a large bowl.
Add the butter, sour cream, garlic and salt to the potatoes. Mash with a potato masher or fork until the desired texture is reached. Add the green onions in and stir to combine. Let cool on counter for about 5 to 10 minutes, until they're cool to touch.
Lay the egg roll wrappers on a clean dry surface and place about 2 to 3 tablespoons of the potato mixture in the center of the egg roll. Top with a strip of cheese and some crumbled bacon.
Brush the outer edges of the egg roll wrapper with the lightly beaten egg, then fold up the egg roll and seal shut. (click HERE for photos on how to fold an egg roll) Repeat with remaining egg roll wrappers.
Heat oil in a deep fryer or heavy bottomed pot to 375 degrees F.
Fry egg rolls for about 2 minutes, or until they reach a golden brown color. Drain on a paper towel lined plate. Enjoy hot, dipped in a cool ranch dressing.
Notes
If using leftover mashed potatoes, you'll need about 2 1/2 cups to 3 cups of mashed potatoes to make this recipe. You do not need to warm the potatoes up before putting in the egg roll wrappers.