Step 1Into a medium bowl, pour 1 cup boiling water over the dried mushrooms and set aside to rehydrate. In another small bowl, pour enough water to cover the bread crumbs and allow to stand.
Step 2Separate the duck confit from the bones and skin and pulse briefly in a food processor until coarsely ground. Remove to a large bowl and set aside. 3. Remove the skin from the duck breasts and coarsely chop the meat with a knife. Pulse the breasts briefly in a food processor, until the mixture resembles ground beef. Do not over-process. Remove the meat from the processor and add to the confit in the large bowl.
Step 3Squeeze the water from the bread crumbs and add them to the bowl. Add the egg, 1 teaspoon salt, one-fourth teaspoon pepper, and the parsley; mix to combine. Form the mixture into meatballs, a scant one-fourth cup each. Roll the meatballs in the flour, coating them lightly, and place them on a tray or baking sheet. The mixture should yield 12 meatballs. Set aside.
Step 4In a large skillet, heat 3 tablespoons of duck fat (or olive oil) over medium-high heat until the fat is hot and a few drops of water splatter when sprinkled in. Brown the meatballs in two batches, turning with kitchen tongs so that they brown evenly, 3 to 5 minutes. (They will be brown but not cooked through.) Set aside on a tray or baking sheet, covered with a paper towel.
Step 5Wipe out the pan and heat 2 tablespoons of duck fat (or olive oil) over medium-high heat. Add the onions, turn down the heat to low and saute until soft, about 4 minutes. Add the garlic and cook an additional 2 minutes. Add the wine, the canned tomatoes plus the juice, the mushrooms and their soaking liquid, the bay leaves and the tomato paste. Bring to a simmer over medium-high heat, then cover and reduce the heat to low. Cook for an hour, checking periodically to make sure the sauce is at a slow simmer and isn't sticking to the bottom of the pan.
Step 6After an hour, add the meatballs to the sauce, covering to coat them. Cover and simmer 30 more minutes.
Step 7Meanwhile, bring 6 quarts of water and 2 tablespoons salt to a boil in a large pot. When the meatballs have simmered 30 minutes, take the pan off the heat and cook the pasta. Cook the pasta al dente, according to the package instructions, and drain. Serve the meatballs and sauce over the spaghetti.