01 - Boil the potatoes in salted water until fork-tender, about 15 minutes. Drain well and return to the pot.
02 - Add butter and milk to the potatoes. Mash until smooth and creamy.
03 - In a skillet over medium heat, sauté the shredded cabbage until tender, about 4 minutes. Add scallions and sauté for 1 minute more.
04 - Stir the cabbage and scallions into the mashed potatoes. Season with salt and pepper. Let cool to room temperature.
05 - Scoop approximately 2 tablespoons of the cooled colcannon mixture, flatten in your palm, place a cube of cheddar in the center, and wrap the potato around the cheese to seal. Shape into a ball. Repeat with remaining mixture.
06 - Roll each ball gently in flour, then dip in beaten egg, then coat with panko breadcrumbs.
07 - Heat 2 inches of vegetable oil in a deep skillet or pot to 350°F. Fry the balls in batches for 2–3 minutes, turning until golden brown and crisp. Drain on paper towels.
08 - Serve hot for maximum cheese pull.