Fill a large pot halfway up with oil and heat to 365 degrees F. Cook the bacon in a large skillet, over medium heat, until crispy on both sides, about 5 to 8 minutes. Transfer onto paper towels to drain, and then roughly chop.
Prepare the mashed potatoes according to package directions and then stir in half of the bacon, 2 tablespoons chopped chives, and half of the cheese. Let cool to room temperature.
To shape the wontons, work with one wrapper at a time. Add about a teaspoon or two of the potato mixture in the center. Brush the edges with egg wash and then seal and crimp into a triangle. Fold 2 points together, brush with egg and pinch to seal. Continue shaping until all the filling has been used.
Once vegetable oil is hot, carefully add a few of the wontons at a time and fry until golden brown, about 3 to 5 minutes. Transfer to a paper towel lined plate and continue frying the rest.
To make the sauce, stir together the sour cream, garlic, salt, pepper and scallions. Set aside.
Arrange the wontons onto a baking sheet, piling them up in the center. Sprinkle with the remaining cheese and bacon and bake in a 350 degree F oven for about 10 minutes, just to melt the cheese.
Remove from the oven and sprinkle with remaining bacon and chives. Serve with scallion sour cream sauce on the side.