To begin, prepare the meatball mixture. In a large bowl, combine the ground meat, finely chopped onion, soaked and squeezed bread roll, egg, mustard, salt, white pepper, and chopped capers (if using). Mix thoroughly with your hands to create a uniform texture. If the mixture feels too wet, add breadcrumbs gradually until it holds together. Cover and refrigerate while preparing the broth.

Prepare the cooking broth. In a large pot, bring the water to a gentle boil. Add bay leaves, black peppercorns, sliced carrot, celery, quartered onion, and a pinch of salt. Let it simmer for 10 minutes to infuse the flavours, then reduce the heat to a low simmer.

Remove the meatball mixture from the refrigerator. Lightly wet your hands and shape the mixture into evenly sized balls, about 4-5 cm in diameter. Gently drop the meatballs into the simmering broth. Cook for 15-20 minutes, ensuring they remain submerged and do not boil, which could break them apart. Once cooked, remove the meatballs with a slotted spoon and set aside. Strain the broth and reserve 500ml for the sauce.

Begin the white sauce. In a medium saucepan, melt the butter over medium heat. Add the flour and whisk continuously to form a smooth roux. Cook the roux for 2-3 minutes, taking care not to brown it, as the sauce should remain pale.

Gradually add the reserved broth to the roux, whisking constantly to prevent lumps. Once all the broth is incorporated, bring the sauce to a gentle simmer. Allow it to cook for 5 minutes until slightly thickened.

Stir in the cream and capers. Add lemon juice, salt, white pepper, and sugar (if using) to taste. Simmer for another 3-4 minutes, adjusting the seasoning to achieve a balance of creamy, tangy, and savoury flavours.

Return the meatballs to the sauce, ensuring they are well coated. Simmer gently for 5 minutes to warm the meatballs and allow the flavours to meld. Avoid stirring too vigorously to keep the meatballs intact.

Serve the Königsberger Klopse with boiled potatoes, rice, or buttered noodles. Garnish with freshly chopped parsley for a vibrant touch. Accompany with a crisp white wine or sparkling water with lemon for an authentic German dining experience. For additional flavour, provide extra capers and lemon wedges on the side.