Soften the bread in the milk for about 30 mins. Melt the butter in a pan, sauté the vegetables and parsley for approx. 5 mins. over a medium heat, salt and set aside. Strain the softened bread, gently squeeze out and combine with the vegetables, along with the egg, cheese and butter. Transfer the mixture to the prepared tin.
Bake for approx. 50 mins. in the centre of an oven preheated to 200°C. Place a few slices of the Salsiz in the gratin and serve the remainder alongside.