Swedish Meatballs

Name: Swedish Meatballs
Ingredients: 1 1/2 cups finely chopped purple onion; 4 1/2 tablespoons unsalted butter; 3/4 pound ground chuck; 3/4 pound ground pork; 1 3/4 teaspoons salt; 1/2 teaspoon freshly ground black pepper, plus a pinch; 1/4 teaspoon ground allspice; 1 cup plain dry bread crumbs; 1/2 cup milk; 1 cup heavy cream; 1 egg, lightly beaten; 4 tablespoons all-purpose flour; 3 1/2 cups beef stock or 2 (14-ounce) cans low-sodium beef broth; 1/4 cup red currant jelly; 1/8 teaspoon ground nutmeg