These loaded Mashed Potato Cakes are my favorite twice-baked potato in patty form, and the best use of leftover mashed potatoes! Great as a side or appetizer.
Cook bacon in a medium skillet over medium-high heat until crispy, stirring occasionally. Drain off grease and transfer to a large bowl (reserving some for garnish.)
In the same skillet, melt the butter. Add the onion and celery; saute until vegetables are tender, about 5 minutes. Stir in the garlic until fragrant, 20 seconds. Transfer to the bowl with the bacon.
Add to the bowl the mashed potatoes, cheese, flour, egg, mustard, pepper, and a few dashes of hot sauce; stir to combine.
Form mixture into 8 (⅓-cup) patties, about ½ to ¾-inch thick. Place them on a lightly greased plate, cover, and transfer to the refrigerator for 20–30 minutes.
Heat oil in the skillet over medium heat. Fry patties until golden brown, 2-3 minutes per side.
Serve immediately with a dollop of sour cream, chives, and reserved bacon.