In a medium skillet over medium-high heat, sautÈ 1 cup of the onion in 11/2 tablespoons of the butter until soft and light golden brown, 4 to 6 minutes. Set aside to cool, then add the onion to a medium mixing bowl along with the ground chuck, ground pork, 11/2 teaspoons of the salt, 1/2 teaspoon of the pepper, the allspice, and the nutmeg.
In a small mixing bowl, combine the bread crumbs with the milk and 1/4 cup of the cream, and allow to sit until the bread crumbs are soft, about 5 minutes. Add the bread-crumb mixture and the beaten egg to the meat mixture and, using clean hands, mix well to thoroughly combine.
Using a tablespoon measure as a guide, scoop the meat mixture into meatball portions, about 1 heaping tablespoon each. Using lightly damp clean hands, roll the meatballs until they are smooth and round. Transfer to a large plate or baking dish while you form the remaining meatballs.
In a medium skillet, heat 1/2 tablespoon of the remaining butter until foamy. Add one-third of the meatballs and cook, turning frequently, until the meatballs are browned on all sides, 6 to 8 minutes total. Using tongs or a slotted spoon, transfer the cooked meatballs to a Dutch oven or heavy large saucepan and repeat with the remaining meatballs, adding another 1/2 tablespoon of butter to the skillet before each batch.
Add the remaining 11/2 tablespoons of butter and the remaining 1/2 cup onion to the skillet and cook until the onion is soft, about 4 minutes. Add the flour and cook, stirring constantly, for 2 minutes. Whisk in the beef broth little by little and cook until the sauce is smooth and thick, about 4 minutes. Transfer the sauce to the Dutch oven or large saucepan and add the remaining 1/4 teaspoon salt, a pinch of black pepper, the remaining heavy cream, and the currant jelly. Be careful when stirring not to break up the meatballs.
Bring the contents of the Dutch oven or large saucepan to a boil over medium-high heat, then reduce the heat so that the sauce simmers. Cook, uncovered, for 45 minutes to 1 hour, until the meatballs are very tender and the sauce is thick and flavorful.
Yield: 4 - 6 servings