Make the filling: Put 1 pound each of beef and pork together through the fine blade of a food chopper twice. In a bowl, combine the meat with 1 cup cooked rice, 1 egg lightly beaten, 1 onion and 2 garlic cloves, both minced, and salt and pepper to taste. Remove 12 large outer leaves from a head of cabbage, reserving the remaining cabbage for another use. Dip the leaves briefly in boiling water to soften and spread them out flat on a work surface. Top each leaf with some of the filling and fold the leaves over the filling, tucking in the ends to make neat rolls. Put 2 pounds sauerkraut in a large kettle with light beer or white wine to cover and heat it gently. In a sauce pan melt 3 tablespoons lard, bacon fat or ham fat, blend in 3 tablespoons flour and cook the roux for 1 to 2 minutes. Blend it into the sauerkraut and bring the liquid to a boil, stirring constantly. Arrange the cabbage rolls on top of the sauerkraut and cook them, covered, in a moderate oven (350?F.) for 2 to 3 hours or until the filling is done. Serve the stuffed cabbage and sauerkraut topped with sour cream.;