Heat the butter and oil in a large pan or saucepan. Briefly sauté the savoy cabbage, add 3 tablespoons of water and cook covered, turning frequently, until soft. Season with salt, pepper and nutmeg. Let cool down.
Line a 26cm springform pan with puff pastry, prick the bottom regularly with a fork. Mix in eggs, milk, cream and cheese, mix in the savoy cabbage. Put in the springform pan. Bake at 170 ° C for 35 to 45 minutes on the lower rack, possibly cover with parchment paper towards the end. Serve fresh from the oven.