Instructions:
- Soak the bread slices in milk until soft. Squeeze out excess milk and crumble the softened bread into a large mixing bowl.
- Add ground meat, egg, salt, pepper, Dijon mustard, and parsley to the bowl. Gently mix until just combined. Roll the mixture into uniform balls (about 1.5 inches diameter).
- Place peeled and quartered potatoes in a saucepan. Cover with cold, salted water and bring to a boil. Cook until fork-tender (15–20 minutes). Drain thoroughly and let steam dry for 2 minutes.
- Rice or mash the potatoes until smooth. Gradually incorporate the cold butter cubes, followed by the warm milk/cream, folding gently until creamy. Season with salt and nutmeg. Keep warm.
- Heat oil/butter in a large skillet over medium-high heat. Sear the meatballs in batches until deeply browned on all sides. Remove and set aside.
- Drain most of the excess fat from the skillet, leaving about 1 tablespoon. Reduce heat to medium and whisk the flour into the remaining fat to create a roux. Cook for 1 minute.
- Slowly whisk in the broth until smooth. Bring to a simmer until slightly thickened. Stir in the heavy cream and Worcestershire sauce. Taste and adjust seasoning.
- Gently return the browned meatballs to the sauce. Cover, reduce heat to low, and simmer for 15–20 minutes until the meatballs are cooked through and coated in the sauce.
- To serve, spoon a generous portion of Kartoffelpüree onto each plate. Ladle the Hackbällchen in cremiger Sauce mit Kartoffelpüree over or beside the mash.