In a large bowl, put the minced meat, season to taste and add the breadcrumbs, the egg, the milk and the chopped parsley. We mix with a fork. When everything is well integrated, we add the caramelized onion, which we always have in the pantry.
We return to work to mix well and prepare to form the meatballs, making small balls the size of pingpong balls and passing them through flour. Fry the meatballs until golden brown in a frying pan with plenty of olive oil. Once golden we pass them to a low saucepan, distributing them on the bottom.
To make the sauce, chop the basil leaves, reserving some to decorate. In a frying pan, put the homemade fried tomato sauce and add the chopped basil, letting it cook and reduce for ten minutes on low heat. Then, we pour the sauce over the meatballs.
Bring to a boil and cover the saucepan., letting it cook for 5 minutes. Then we turn the meatballs over, turn off the heat and let them rest for another 5 minutes with the lid on, so that they finish cooking and are ready to take to the table.