Step 1: Prepare the Mussels

1. Rinse the mussels under cold water, scrubbing the shells to remove any debris. Remove the “beard” by pulling it firmly. Discard any mussels that are cracked or remain open after tapping them gently.
2. In a large pot, heat olive oil over medium heat. Add the mussels and pour in the white wine or chicken broth. Cover and steam for 3–5 minutes, or until the mussels open. Remove from heat and allow them to cool. Discard any mussels that do not open.

Step 2: Prepare the Stuffing

1. In a mixing bowl, combine the breadcrumbs, parsley, thyme, garlic, chopped sausage (if using), Parmesan cheese, salt, and pepper. Mix well.
2. Add the beaten egg and olive oil to the mixture, stirring until the stuffing holds together. Adjust the consistency by adding more breadcrumbs or olive oil if needed.

Step 3: Prepare the Mussels for Stuffing

1. Remove one half of the shell from each mussel, leaving the mussel attached to the other half.
2. Place a small spoonful of the stuffing mixture onto each mussel, pressing it gently to adhere. Set the stuffed mussels aside.

Step 4: Make the Tomato Sauce

1. In a large skillet, heat olive oil over medium heat. Add the onion and garlic, sautéing until softened, about 3 minutes.
2. Stir in the crushed tomatoes, sugar, red pepper flakes, smoked paprika, salt, and black pepper. Simmer the sauce for 10 minutes, allowing the flavors to meld.
3. Stir in the fresh basil and adjust seasoning to taste.

Step 5: Assemble and Bake

1. Preheat your oven to 375°F (190°C).
2. Spread a thin layer of the tomato sauce in the bottom of a large baking dish. Arrange the stuffed mussels on top, ensuring they are evenly spaced.
3. Spoon a small amount of tomato sauce over each stuffed mussel. Cover the dish with aluminum foil.
4. Bake for 15–20 minutes, or until the stuffing is golden and heated through.

Step 6: Serve and Garnish

1. Remove the mussels from the oven and transfer to a serving platter. Garnish with fresh parsley and serve with lemon wedges and crusty bread for dipping into the sauce.
2. Serve warm and enjoy the rich, Mediterranean flavors!