Peel and cut potatoes into equal-sized chunks about 2 inches each. Place in a large pot with cold water and add 1 tablespoon of salt, covering by about an inch. Bring to a boil over high heat, then reduce heat to medium and simmer for 22-25 minutes until fork-tender.

While potatoes cook, combine ground beef, egg, breadcrumbs, paprika, salt, and pepper in a bowl. Mix gently for about 30 seconds until just combined. Roll into balls about the size of a golf ball, keeping them uniform in size.

Heat a large skillet over medium-high heat with 1 to 2 tablespoons of oil. Add meatballs in a single layer with about 1 inch between each, working in batches if necessary. Brown on all sides for 8-10 minutes total. Remove and set aside.

In the same skillet, add diced onions and sauté for 3-4 minutes until softened. Add garlic and cook for 30 seconds, stirring constantly. Stir in tomato paste and cook for 1 minute, stirring frequently.

Pour in heavy cream and vegetable broth, stirring to combine and scraping up browned bits. Season with salt and pepper. Return meatballs to pan, reduce heat to medium-low, cover, and simmer for 8-10 minutes.

Drain potatoes and reserve 1/2 cup cooking water. Return potatoes to hot pot and let sit for 1 minute. Add butter, milk, and about 1/3 cup reserved water. Mash until smooth, adding more water as needed. Season with salt, pepper, and nutmeg.

Serve mashed potatoes on plates, top with meatballs and cream sauce, and garnish with fresh parsley.