Make the sausage: In a large skillet over medium heat, add 2 tablespoons oil; add 1⁄4 cup onion and a pinch of salt and cook, stirring, until the onion is well softened, 7–10 minutes. Let cool completely. Mix with the 2 tablespoons cream, the oats, egg, chopped sage, 3⁄4 teaspoon salt, and teaspoon pepper. Add 1 pound ground pork and the pig’s blood and mix thoroughly. Cover and refrigerate.
Make the Bolognese: Preheat the oven to 325°. To a piece of cheesecloth, add the thyme and rosemary, sage leaves, and cloves. Enclose the spices fully, then seal with kitchen twine or the ends of the cheesecloth. Set aside.
In a large Dutch oven over medium-high heat, add 2 tablespoons oil. Add the remaining pork and season with 3⁄4 teaspoon salt; cook, stirring occasionally, until well browned, 5–7 minutes. Transfer the pork and juices to a bowl. Lower the heat to medium and add 3 tablespoons olive oil. Add the remaining onion, carrots, and celery; season generously with salt and cook, stirring occasionally, until the vegetables are softened slightly, about 3 minutes. Stir in the garlic, tomato paste, and chile flakes, and cook 2 minutes. Return the pork and juices to the pot, and stir in the wine. Bring to a simmer over high heat and cook until the wine is reduced by a third, 6–8 minutes. Add 2 1⁄2 cups water and return the sauce to a simmer. Stir in the nutmeg and the herb bundle and cover the pot. Transfer to the oven and let cook 2 hours.
Meanwhile, make the pasta: Combine the ours on a clean work surface. Form a deep well in the center and add the eggs, pig’s blood, and salt. Mix with a fork, gradually incorporating the our until a dough forms. Knead by hand until the dough is soft and smooth, adding more our to the work surface or your hands as needed if sticky, 7–10 minutes. Flatten the dough into a 1-inch-thick square. Wrap in plastic and let rest at room temperature for 30 minutes or up to 1 day in the refrigerator.
Cut off a piece of dough about 1 1⁄2 inches wide. Flatten to fit through the widest setting on a pasta machine. Guide the piece through the rollers, flouring as needed. Fold into overlapping thirds like a letter and repeat, leading with the widest side. Switch to the next narrowest setting and guide the dough through once. Repeat until you’ve reached the second thinnest setting on the machine.
Cut pasta into 12-inch sheets. Layer 2 or 3 sheets, dusting each generously with semolina before layering to be sure they don’t stick together. Roll the dough from both ends tightly like a scroll so the short sides meet in the center (like a pair of binoculars). Using a very sharp knife, slice the rolls into wide, 3⁄4-inch-thick noodles. Shake the noodles loose, then portion into 3- to 4-ounce nests. Place the nests on a baking sheet lightly floured with semolina and set aside.
Toast the bread crumbs. In a large skillet, heat 1 tablespoon olive oil over medium-high heat. Add the bread crumbs and a generous pinch of salt. Cook, stirring frequently, until browned and crispy, 8–10 minutes. Remove to a bowl.
Retrieve the sauce (the meat should be tender and the sauce noticeably thickened). Set it back on the stovetop over low heat. Stir in the remaining heavy cream and the blood sausage, breaking the sausage up into small pieces. Let simmer until the sauce has a velvety texture, 20–30 minutes. Taste and adjust the seasoning with salt and pepper or a few more drops of red wine as needed. Remove the herb bundle and discard.
Meanwhile, bring a large pot of water to a boil and season it generously with salt. Add the prepared pasta and cook until al dente, 3–4 minutes. Drain, reserving a few tablespoons of the cooking water, then return the pasta to the pot or a serving bowl. Add spoonfuls of the sauce to the noodles until it moistens and clings without covering them entirely, thinning the sauce with 1 or more tablespoons of the reserved pasta water if necessary. Taste and adjust the seasoning as needed.
Serve topped with grated Parmigiano-Reggiano and toasted bread crumbs to taste.