For the tomato casserole, boil milk with salt and butter, add the flour and stir until the dough separates from the bottom of the pot. Then let the dough cool down.
Whisk the yolks and stir into the cooled dough. Add the sausage and herbs. Beat egg whites until stiff and fold into the dough. Cut the tomatoes into slices and salt them, line a buttered baking dish with them.
Spread the dough over the tomatoes and put the dish into the preheated oven. Bake at 200 °C for about 30 minutes.