Mini Swedish Meatballs and Mashed Potatoes

Name: Mini Swedish Meatballs and Mashed Potatoes
Ingredients: 1 lb. russet potatoes, peeled and chopped; 4 tbsp. butter; 1/4 c. heavy cream; kosher salt; Freshly ground black pepper; 1 slice white bread, crumbled; 1/4 c. whole milk; 3 tbsp. butter, divided; 1/2 c. finely diced onion; 2 cloves garlic, minced; 1/2 lb. lean ground beef; 1/2 lb. lean ground pork; 1 large egg, beaten; 1 tsp. kosher salt; 1/2 tsp. Freshly ground black pepper; 1/4 tsp. ground allspice; 1/4 tsp. ground nutmeg; 2 tbsp. all-purpose flour; 1 1/2 c. warm beef broth; 2 tbsp. heavy cream, optional; Freshly sliced chives, for garnish