1. For the tomato sauce, sauté the two minced onions in a good pour of olive oil in a Dutch oven or very large saucepan, seasoning them with a bit of salt and a few generous turns of black pepper, stirring frequently – until the onions start to wilt. Add the garlic and cook until the onions are completely soft and translucent.
2. Add the canned tomatoes, the tomato paste, 1 1/2 teaspoons salt, dried oregano, red pepper flakes, the bay leaf and the sugar, and let simmer for 10 to 12 minutes over low heat, stirring everyone so often. Set aside.
3. To make the meatballs, sauté the onion in some olive oil in a large skillet, seasoning with a bit of salt and black pepper, stirring frequently, until the onions start to wilt. Add the garlic, and cook until the onions are completely soft and translucent. Remove from heat, scrape into a large bowl, and let cool to room temperature.
4. To the bowl, add the ground beef and pork, the eggs, cheese, parsley, herbs, 2 teaspoons salt, a few generous turns of black pepper, the fennel seeds, the breadcrumbs, and the milk. Use your hands to mix everything together thoroughly.
5. Preheat the oven to 350ºF (180ºC) and line two baking sheets with parchment paper, or grease them with olive oil.
6. Form meatballs slightly less than the size of unshelled walnuts, and place them evenly spaced apart on the baking sheets. Bake the meatballs for 15 minutes, then remove from the oven, pluck out the bay leaf, and slide them into the tomato sauce. You can also fry the meatballs in olive oil in batches, in a large skillet until cooked through, although it can be quite messy.
7. Heat the sauce with the meatballs in it until everything is warmed through. If the sauce is very thick, it can be thinned with a bit of warm water.
Note: If you like your meatballs sandwiches more “sloppy”, or extra-saucy, leave out about a dozen of the meatballs. They can be frozen for another use.
To make sandwiches, take crusty French or Italian bread, cut it open almost all the way through. Slice some of the meatballs in half and put them between the bread, pressing down with a fork to meld them with the bread. Top with slices of cheese and heat in a hot oven (about 200ºC), or under a broiler, until the cheese melts.