Slice leeks into 3 cm rounds and rinse well
Fry leeks in a splash of olive oil for 5 minutes on each side until just tender
Make the sauce by melting butter in a saucepan, then whisking in the flour
Cook flour mixture for 1 minute, then slowly add the milk, mixing until smooth and thickened
Stir in cheddar, gochujang and gochugaru until the cheese melts and the sauce turns glossy and bright orange
Preheat oven to 200C / 400F
Transfer leeks to a small baking dish and pour the sauce over
Top with panko crumbs and sesame seeds
Bake at 200C for about 20 minutes, or until the top is golden and crisp
Serve hot
