Heat a large pot that has a lid on medium heat with olive oil.
Now add the onions, garlic and chili flakes. When cooked halfway, about 3 minutes, turn to high heat and add the mussels.
Cook mussels for about 1-2 minutes, now add the white wine and allow to cook for 1 minute.
Add the tomato sauce and cover. Let steam for about 5-8 minutes until mussels open.
When mussels are open, add the butter, parsley and basil. Adjust seasoning with salt and pepper.
Enjoy the mussels with the baguette and a nice glass of wine.