For the risotto: Heat the stock with 1 1/2 cups water and the saffron and keep warm. Heat 2 turns of the pan EVOO in a pot and cook the pancetta to render, 3 minutes. Stir in the garlic and onions and cook until softened, 3 to 4 minutes, and then add the rice and toast 1 minute. Pour in the wine and cook until evaporated, then begin adding the warm saffron liquid a few ladlefuls at a time, stirring frequently to develop the starches. The risotto will take exactly 18 minutes time from first addition of liquids. Stir in the cheese and butter and remove from the heat.
For the meat and mushroom filling: Heat the stock in a small pot along with the mushrooms, and chop once reconstituted (keep the liquid). Melt 2 tablespoons of the butter in a large skillet and cook the onions to a light caramel color, then transfer to a plate. Melt the remaining 1 tablespoon butter, raise the heat slightly and stir in the chicken livers. Sprinkle with the thyme, some salt and pepper and cook 3 to 4 minutes. Pour in the sherry and transfer the livers to a plate.
Pour the EVOO into the center of the skillet. Once the oil is hot, brown the beef and sausage, breaking up the meat as it cooks. Stir in the garlic and cook 1 to 2 minutes. Return the onions and livers to the skillet along with the tomato paste, mushrooms and mushroom soaking liquid. Simmer over low heat to thicken and combine the flavors, about 3 minutes.
To assemble: Preheat the oven to 400 degrees F. Mix together the mozzarella, peas, basil and tomatoes in a small bowl. Grease a baking mold or ovenproof bowl with butter and dust with breadcrumbs. Fill the mold evenly with half of the risotto and top with the meat sauce. Create a small well in the center, and fill with the mozzarella, peas and tomatoes. Layer the rest of the risotto on top and smooth the surface. Dot the top with butter and remaining breadcrumbs.
Bake 45 minutes. Let cool on a rack while in the mold 15 minutes before loosening the edges with an offset knife. Place a plate on top of the mold, invert, and serve.