Peel the potatoes and cut into equal-sized pieces, about 2 inches each. Place in a large pot with lightly salted water and bring to a boil. Cook for 20 to 30 minutes until fork-tender. Reserve 2/5 cup of cooking water before draining.

In a large bowl, gently combine ground beef, egg, breadcrumbs, paprika, 1 teaspoon salt, and 1/2 teaspoon black pepper. Mix just until combined, avoiding overworking the meat.

Form the mixture into meatballs about 1 inch in diameter, keeping them uniform in size for even cooking.

Heat 1 tablespoon oil in a large skillet over medium heat. Add meatballs and brown on all sides for about 10 minutes total. Remove to a plate and set aside.

In the same skillet, saute the diced onion for 2 to 3 minutes until translucent. Add minced garlic and cook for 1 minute until fragrant.

Stir in tomato paste and toast for about 1 minute to intensify the flavors.

Pour in heavy cream and vegetable broth, stirring to combine. Season with remaining salt and pepper to taste.

Return meatballs to the skillet, cover with a lid, and simmer over medium heat for 5 to 10 minutes until the sauce thickens and meatballs are cooked through.

Add butter, milk, and reserved cooking water to the drained potatoes. Mash until smooth and creamy. Season with salt, pepper, and nutmeg to taste.

Serve meatballs over mashed potatoes, spooning plenty of sauce on top. Garnish with freshly chopped parsley.