Mix the ground meat with the roll and the other ingredients, and make 8-10 rounds balls. Heat the butter in the pot, and add the flour to make a paste. Add in the stock stir it to make it smooth. Into this, you put the balls, so that they are almost covered by the sauce. Strew the onion over it. Add lemon juice. Cover and Cook over very low heat (do NOT boil), occasionally shaking the pot to rotate them. (Move the dish around, but don't touch them, or open the dish). They should be done on the inside (no longer red inside). After the kloepse have been taken out of the pot, you can stir in the optional egg yolk and butter to the sauce, if desired, before serving the sauce. Served with the sauce salt-potatoes.
Done in 20-30 minutes.