Preheat the oven to 400 degrees.
Put the bread crumbs, milk, egg, scallions, parsley, ricotta, and Grana Padano in a large bowl. Stir until smooth.
Add the beef and pork, 1 ½ teaspoons salt, and the nutmeg. Mix with your hands to combine and form into four 4-inch-long mini-meat loaves.
Spread some flour in a shallow bowl for dredging.
Heat a nonstick skillet over medium-high heat. Add the olive oil.
Dredge the meat loaves lightly in flour, and add to the skillet. Brown all over, about 5 minutes.
Scatter the mushrooms between the meat loaves. Cook and stir until they begin to brown and wilt, about 5 minutes.
Pour the marinara over the meat loaves, and add ½ cup water. Press the basil sprigs into the sauce.
Cover, and bake until it’s bubbling, about 15 minutes.
Uncover, bake until the meat loaves are crusty and cooked through, about 15 minutes more, remove the basil sprigs, and serve.