For the meatballs: Combine the Parmesan, ricotta, breadcrumbs, milk and egg in a medium bowl and stir well to combine and allow the breadcrumbs to absorb the liquid. Add the pork, sausage and salt and use your hands to mix gently to combine.
Heat a medium straight sided skillet over medium heat. Add enough oil to cover the bottom of the skillet. Roll heaping tablespoons of the meat mixture into balls and place in the hot oil. Add as many as the skillet will allow without overcrowding, working in two batches if needed. Brown the balls on all sides, rotating as needed, about 8 minutes. Remove the balls to a plate and pour off the oil from the skillet. Add the marinara and 1/4 cup water to the skillet and bring to a simmer. Return the balls to the sauce and cover the skillet. Allow to simmer for 15 minutes. Remove from the heat.
For the salad: Meanwhile, toss together the arugula, Parmesan shavings, olive oil and lemon juice in a medium bowl.
Spoon 5 or 6 meatballs into a bowl, then top with some of the salad and serve. Repeat to make 4 more servings.