01 - Pat the chopped kimchi dry with paper towels to remove excess moisture. If desired, mix with gochujang and chopped green onion for additional flavor.
02 - Lay out bread slices on a clean surface. Spread softened butter evenly on one side of each slice.
03 - Flip bread so unbuttered side faces up. Place 1 slice cheddar and 1 slice mozzarella on two slices. Distribute chopped kimchi evenly over cheese, then top with remaining cheddar slices.
04 - Close sandwiches with remaining bread slices, buttered side facing outward.
05 - Heat nonstick skillet or griddle over medium-low heat. Place sandwiches in pan and cook for 3–4 minutes per side, pressing gently with spatula until golden brown and cheese is fully melted.
06 - Remove from heat and let rest for 1 minute. Slice diagonally and serve hot.