01 - In a large bowl, mix together mashed potatoes, shredded cheddar cheese, green onions, bacon bits if using, egg, flour, garlic powder, salt, and black pepper until the mixture is evenly combined.
02 - Divide mixture and shape into 8 patties, each about 3/4 inch thick, using clean hands or a scoop for uniform size.
03 - Spread breadcrumbs onto a plate. Coat each patty thoroughly by pressing both sides into the breadcrumbs.
04 - Melt unsalted butter together with vegetable oil in a large nonstick skillet set over medium heat.
05 - Carefully place patties into the skillet in batches and fry for 3 to 4 minutes per side, or until crisp and golden brown. Add extra oil if necessary between batches.
06 - Transfer the cooked patties to a plate lined with paper towels to absorb excess oil. Serve immediately, optionally garnished with sour cream, fresh chives, or preferred breakfast sauces.