Tomatoes and chorizo mussels

Name: Tomatoes and chorizo mussels
Ingredients: 1 yellow onion, finely chopped; 3 garlic cloves, finely chopped; Olive oil; 250 g PEPE sausage from the Pork Shop Charcutiers (or chorizo), diced; 4 large tomatoes, diced (save one for last); 1 large handful fresh parsley, finely chopped + a little for serving; 1/4 cup white wine; 2 tablespoons tomato paste; 1 tablespoon sugar; 1/2 teaspoon dried oregano; 2 lb fresh mussels cleaned and sorted; 1 cup finely grated Pecorino Romano cheese; Salt and pepper from the mill