To make Swedish potato sausage, a dish commonly known as "potatis korv" in Sweden, process 5 pounds peeled potatoes, 1 pound peeled onions and 1 pound of boneless pork shoulder butt roast in a food grinder. Coarsely grind the ingredients, alternating between the three.
Transfer the ground mixture to a bowl and combine it with 1 pound of ground beef. In a separate small bowl, combine dry ingredients and 1 to 2 tablespoons of all-purpose flour, 1 to 3 tablespoons salt, 1 tablespoon ground black pepper, 1 teaspoon ground allspice and 1/2 teaspoon ground nutmeg. Sprinkle the dry ingredients over the potato and meat mixture, add 1/4 cup of milk to the bowl and mix everything together well until it's all combined. Form the homemade Swedish potato sausage into patties or stuff it into prepared casings. Use the sausage right away or store it in the freezer.
Pan-fry sausage patties or simmer the sausages in a frying pan filled with 1 1/2 inches of water. Simmer the sausages over medium heat for 10 to 12 minutes before draining the water and adding oil or butter to the pan to brown the sausages over medium or medium-high heat. Alternatively, grill the simmered sausages over medium heat until they are golden.