Traditional British boxing day staple made from leftover mashed potatoes and shredded Savoy cabbage, pan-fried in foaming butter until a deep golden, crispy underside crust forms.
In a bowl, mix cold mashed potatoes, shredded greens, softened onion, sea salt, and plenty of black pepper until combined but still rustic.
Melt butter or beef dripping in a large cast-iron frying pan over medium-high heat. Add the potato mixture, pressing flat with a spatula to form a thick cake.
Cook undisturbed for 8-10 minutes until the underside forms a deep golden, crunchy crust (listen for the bubbling and squeaking sound).
Invert onto a plate, slide back into the pan, and fry the other side for 6 minutes until equally crisp. Cut into wedges and serve with fried eggs or cold cuts.