Start by melting butter in a skillet over medium heat. Add the finely diced onion and cook for about 7 to 8 minutes, stirring occasionally until soft and lightly golden.

Add minced garlic in the last minute and stir through. Remove from heat and let cool for at least 5 minutes.

In a large mixing bowl, add cold mashed potatoes, sautéed onion and garlic mixture, shredded cheddar, eggs, flour, salt, black pepper, smoked paprika, and chives. Mix until a thick mixture forms.

If mixture feels too sticky, add a tablespoon more flour. Avoid overworking the mixture to maintain texture.

Lightly dust hands with flour, scoop out approx 1/3 cup for each cake, roll into a ball, and then flatten to 3/4 inch thick patties.

Place patties on a parchment-lined tray. Chill in the fridge for 10 minutes if the mixture feels soft.

Heat olive oil in a non-stick skillet over medium heat. Cook 3 to 4 cakes for 4 to 5 minutes on the first side.

Flip carefully and cook the second side for another 4 minutes until golden. Transfer to a plate lined with paper towels and repeat.

Serve immediately while crispy, optionally with sour cream or hot sauce.