Anelletti al forno is a classic Sicilian baked pasta dish that's made with small pasta rings and hearty ragù. It's a crowd-pleasing dish that's best described as SpaghettiOs for adults.
Heat oil and butter in a 3 to 4-quart saucepan over medium heat. Once the oil is heated and the butter is just melted, add the onions, carrot, and celery to the pan. Add a pinch of salt. Cook until just pale golden and tender (about 15 minutes). When the vegetables are tender, optionally grate in a small amount of nutmeg (about 1/2 teaspoon) and add the optional chili flake.
Add half of the ground beef and cook until the meat is just brown. Add the second half of the ground beef. When all of the beef is browned and a fond forms at the bottom of the pan, pour in the wine and scrape off the fond. Cook until almost all of the wine evaporates.
Add the tomato puree along with any juices from the puree and cook, simmering slowly, for 40 minutes. Add water if the sauce gets too thick. (You don't want the sauce to stick and burn.) At the end of the cooking time, the ragù should be thick enough to slowly drop off a spoon. Once cooked, take the ragù off the heat.
Preheat the oven to 400°F / 200°C.
Cook the pasta in a relatively large pot until just al dente - about 2 to 3 minutes less than the package instructions. Make sure you stir the anelli frequently so that it doesn't stick to the bottom of the pan and burn. Stop cooking the pasta when it's just a little firm in the center. Drain and let the pasta cool slightly.
Place the anelli, ragù, half of the mozzarella and half of the grated cheese into a mixing bowl and thoroughly combine. Butter a baking dish and coat it lightly with the breadcrumbs. Pour in the pasta/ragù mixture and even out the top. Top with the remaining mozzarella, grated cheese and 1 tablespoon of breadcrumbs.
Bake the pasta for about 30 to 45 minutes until golden brown. Remove from the oven and serve to your hungry guests or family.