01 - In a large mixing bowl, blend the mashed potatoes, cheddar cheese, bacon, green onions, egg, flour, garlic powder, black pepper, and salt until the mixture is uniform.
02 - Divide the potato mixture into 8 equal mounds and gently shape each into a patty approximately 3/4-inch thick.
03 - Spread the panko breadcrumbs on a plate. Lightly dredge each formed cake in breadcrumbs, pressing gently to adhere.
04 - Heat the unsalted butter and vegetable oil together in a large skillet over medium heat until shimmering.
05 - Place the potato cakes into the skillet in batches, avoiding overcrowding. Cook for 3 to 4 minutes per side until crisp and deeply golden. Transfer to a plate lined with paper towels to drain excess oil.
06 - Serve the potato cakes immediately, hot, topped with extra green onions or a spoonful of sour cream if desired.