Quarter the cabbage, remove the core and shred the leaves. Blanch in a pan of boiling salted water for 3 mins, then hold under a cold tap to cool. Drain well. Heat the goose fat in a pan and sauté the shallots, rosemary sprig and garlic cloves for 5 mins, until golden. Discard the garlic and rosemary, toss in the cabbage, stir-frying until reheated. Season and serve.