This is a Sunday supper kind of dish, as it's best if it simmers a long time. I love the use of giblets here, and I encourage you to save some for this recipe. Any bird giblets will work, and if you feel unusually squinchy about, say, livers, leave them out -- although they are traditional. You could also use venison liver and heart here, or those from rabbits or really any other animal. And yes, you can use all ground meat. But that would be boring... The mushrooms add a lot. Use them. And don't use fresh, as you want the mushroom soaking water. I used porcini, but morels or any "woodland mix" you buy in the supermarket is fine.
Break up the mushrooms and submerge them in 1 to 2 cups of hot water. Let them sit while you proceed.
Pulse the onion, celery, carrot and garlic in a food processor until you get somewhere between a fine mince and a paste. Don't puree it. Set the vegetables aside in a bowl for now.
Heat the olive oil in a large Dutch oven or heavy lidded pot set over medium-high heat. When the oil is hot, add the giblets and the ground meat. Brown them well, sprinkling some salt over them as they cook. When they are close to being done, stop stirring them so a crust, what the French call a "fond," forms on the bottom of the pan. Brown is good, black not so much. So watch your heat. When it forms, remove the meats and set aside.
Add the vegetables to the pot. Let the moisture from the vegetables soften the meat crust in the pot. Salt them as they cook. Use a wooden spoon to scrape up all the browned bits. Cook over medium heat until the vegetables soften well, and then let another crust form.
While the vegetables are cooking, mince the mushrooms. Keep the mushroom soaking water, and strain it if there's debris in it. When the crust has reformed in the pot, add the mushrooms and the cup of sherry. Use the wooden spoon to scrape up the browned bits again. Let all the sherry cook away until yet another crust forms.
Add the nutmeg, bay leaves, cloves, and 1 cup of the mushroom soaking water. Scrape up the crust one last time. Bring the sauce to a simmer and add the juice/sauce from the jar of whole tomatoes. Crush the tomatoes by hand into the pot. Return the meats to the pot, stir well, add salt to taste and simmer, partially covered, for at least 90 minutes. You want the gizzard bits to be fairly tender.
To finish, get your water boiling for the pasta. Turn the heat to low on the sauce and add the cream. Bring the sauce back to a bare simmer and when the pasta is ready, grind black pepper over the sauce. I like to put the pasta in a large bowl, add one ladle of the sauce over it and toss to coat. I then give everyone some pasta and add a bit more of the sauce on each person's plate. Grate some cheese over everything and you're good to go.
Notes
For pasta, spaghetti, tagliatelle, pappardelle, or any substantial, short pasta shape is a good choice. Nothing too light -- vermicelli's too light. Polenta would be another great accompaniment.