Beer Braised Cabbage with Bacon by hip pressure cooking

– 1 tablespoon butter
– 1 medium onion, sliced into strips
– 3.5 oz (100 g) bacon or smoked pancetta, cubed
– 1 medium savoy cabbage (about 1.5 lbs or 750 g), sliced into strips
– 1 cup (250 ml) beer