For the apple semolina casserole, prepare the semolina. Boil the milk with a pinch of salt and stir in the semolina until it thickens. Then let the semolina cool down.
Then make a drift. Cream butter, sugar and 3 yolks. If needed, add a pinch of salt, vanilla (e.g. from a vanilla bean) or grated lemon zest.
Stir the cooled semolina into the egg white mixture. Beat the egg whites until stiff and gently fold into the mixture. Wash, peel and core the apples and cut them into thin slices.
Sprinkle with lemon juice to prevent them from turning brown. Pour the mixture into a greased baking dish and garnish with the apples.
Bake the casserole for 20-30 minutes at 170 degrees.