Soak crumbs in 1 cup cream in a medium bowl until thick. Meanwhile, cook onion in 3 tablespoons butter in a 10-inch heavy skillet, stirring occasionally, until softened, about 6 minutes, then stir into crumb mixture. Add meats, dill, cloves, 1 1/2 teaspoons salt and 1 teaspoon pepper and combine well with your hands. Form mixture into 1 1/4-inch meatballs.
Preheat oven to 350F with rack in middle.
Heat oil in skillet over medium-high heat until hot, then brown meatballs in 5 batches, shaking skillet to maintain shape, and transfer as browned to a 3- to 4-qt baking dish. Add 3/4 cup water to skillet and boil, stirring up brown bits, until reduced to about 1/2 cup. Add remaining 1/2 cup cream and 5 tablespoons butter and stir until butter is just melted. Remove from heat, then stir in fresh dill and pour over meatballs. Bake until meatballs are no longer pink within, 8 to 10 minutes.
Make ahead: Meatballs can be made 3 days ahead, without fresh dill, and chilled (covered) once cooled. Just before serving, spread meatballs out in a large baking dish, then stir in fresh dill and heat in a 350F oven until heated through, about 8 minutes.