Preparation

• In a stand mixer fitted with the paddle attachment, soak the bread in the milk until softened, about 5 minutes. Mix on low speed until uniform, about 30 seconds. Add the beef, pork, onion, and egg and mix on low speed until incorporated. Sprinkle in the allspice, nutmeg, 1-/2 tsp. salt, and 1/2  tsp. pepper, increase the speed to medium, and mix until incorporated, about 30 seconds.
• Set a small bowl of cold water nearby and, occasionally moistening your hands, gently roll 1-1/2-oz. portions of the meat into balls; you should get about 25.
• Heat a 12-inch skillet over medium-high heat. Add 1 Tbs. each of the butter and oil. When the butter is melted, add half of the meatballs. Reduce the heat to medium and cook, undisturbed, until browned on the bottom, 2 minutes. Flip and brown the other side, 1 to 2 minutes more. Transfer to a paper-towel-lined plate, and repeat with the remaining meatballs.
• Pour off the fat, return the skillet to medium heat, and add the remaining 1 Tbs. each butter and oil. Add the flour, and cook, stirring with a wooden spoon, until the mixture turns light brown, about 1 minute. Whisk in the chicken broth and heavy cream, and bring to a boil. Return the meatballs to the pan, reduce the heat to medium, and simmer, shaking the pan occasionally, until the meatballs cook through (160°F) and the sauce thickens, 8 to 10 minutes. Season the sauce to taste with salt and pepper.
• Meanwhile, in a food processor, pulse the cranberries, sugar, lemon zest and juice, ginger, and 1/4 tsp. salt until finely chopped. Add more sugar and salt to taste.
• Transfer the meatballs to a serving bowl. Stir the herbs into the sauce, and pour over the meatballs. Serve with the cranberry relish on the side.