Meatballs with Lemon

Meanwhile, soak the roll in warm water. Peel the onions, cut 1 onion into quarters, finely chop the other and sauté chopped onion in 20 grams (approximately 1 1/2 tablespoons) butter. Rinse the lemon in hot water, wipe dry and finely grate zest. Squeeze the bread and tear into bite-sized pieces. Mix half the lemon zest with the ground veal, egg whites, cooked onions and squeezed bread and season with salt, pepper and marjoram. Shape mixture into small meatballs with wet hands. Cook the meatballs in simmering broth with the onion quarters, bay leaf and allspice for about 15 minutes. Remove meatballs and set aside, reserving cooking liquid. Cook flour in 20 grams (approximately 1 1/2 tablespoons) melted butter until smooth and add about 500 ml (approximately 2 cups) of cooking liquid. Add capers, mustard, and cream and simmer over low heat, about 10 minutes. Squeeze juice from lemon and add to taste with salt and pepper. Stir in egg yolk (do not boil!). Add the meatballs to the sauce, heat through and then spoon onto warmed plates with the sauce. Sprinkle with remaining lemon zest and dill. Toss potatoes in remaining hot butter, season lightly with salt and serve with meatballs.