Instructions:
- In a large bowl, gently combine the cooled mashed potatoes, grated cheese, 1/4 cup flour, egg yolk, chives, salt, and pepper. Mix just until everything is uniformly incorporated—do not overwork it.
- Cover the bowl tightly and chill the mixture in the refrigerator for a minimum of 1 hour. This step is vital for firming up the mixture.
- Prepare a three-dish breading station: Dish 1 with 1/2 cup flour, Dish 2 with the two beaten eggs, and Dish 3 with the Panko breadcrumbs.
- Scoop about 1.5 tablespoons of the chilled mixture, roll into a tight ball, and slightly flatten into a disc or torpedo shape.
- Coat each puff first in the flour (shaking off excess), then dip completely in the egg wash, and finally press firmly into the Panko breadcrumbs to ensure an even, thick coating.
- Heat the frying oil in a sturdy saucepan to 350°F (175°C).
- Carefully lower 4–5 puffs into the hot oil, ensuring not to overcrowd the pan. Fry for 3–4 minutes, turning gently, until they are deep golden brown and crispy.
- Remove the puffs with a slotted spoon, place them on a wire rack lined with paper towels to drain excess oil, and season lightly with salt immediately. Serve warm.