Minced pork shoulder and pork fat, 80% to 20% ratio. I don't use breadcrumbs but make my own rusks. Plain flour (500g), water(250ml) baking powder(20g). Bake, 230c for 10 minutes, and grind. Pork to rusk ratio should be around 90% to 10%.
Salt, pepper and sage to taste.
Mix everything together. Fry a little and taste. Adjust seasoning accordingly. When you are happy, stuff into skins. These are available fresh from any pork vendor, will need cleaning, or frozen in Makro.