For the meatball parm: Preheat the oven to 185 degrees F.
Combine the bread and milk in a bowl and leave to soak for 20 minutes.
Meanwhile, in a small saute pan over medium-low heat, sweat the garlic in the olive oil until softened but not browned. Add the onion and parsley and cook until the onion is translucent. Remove from the heat to cool.
Combine the soaked bread and the cooled onion-garlic mixture in a large bowl. Add the beef, sausage, veal, egg, Parmesan and a generous sprinkling of salt and mix by hand. Divide into 6-ounce balls, then shape into burger-like patties.
Dredge the patties in flour and sear in canola oil in a large skillet over medium-high heat; you are just browning the patties, not cooking them through. Transfer the patties to a baking dish, cover with tomato compote and sprinkle with Parmesan. Cover with foil and bake for 45 minutes.
For the sandwich: Add a meatball to each roll, garnish with Parmesan and torn basil leaves and serve.