Preheat your oven to 180 C. Microwave the bell peppers on High for 2 minutes to soften slightly. Cut bell peppers in half, lengthwise. Remove seeds and membranes, leave the stem intact for visual purpose.
Heat oil in a large skillet over medium high heat. Add sausage to skillet and cook 4 minutes, stirring to break into small pieces. Add onion to skillet, stirring occasionally, until sausage is cooked and onion is tender, about 3 minutes. Remove sausage mixture from pan.
Add cornmeal to the same skillet cook 1 minute, stirring constantly then add broth, milk, and 3/4 teaspoon of the salt, bring to a boil. Cover, reduce heat to medium, and cook, stirring occasionally, until liquid is absorbed, about 20 minutes. Stir in parsley, sausage, and half of the cheese. Divide mixture evenly among bell pepper halves. Place side by side on a baking sheet. Sprinkle with remaining mozzarella cheese.
Bake for 30 minutes or until the cheese is browned and the peppers are tender.
While the peppers are cooking, whisk the olive oil, vinegar, black pepper, and remaining salt in a medium bowl, add the tomatoes and basil, toss to coat. Serve over peppers with bread or a salad on the side for a complete meal.