Brush the mussels under running water. Throw away opened mussels that do not close under water or when you tap them lightly. In a large saucepan in the olive oil, sauté the onions, leeks, chilli peppers and garlic, add the ready-to-cook mussels and cook over high heat for 5 minutes until they open. Now pour the white wine over it and cook for another three minutes over high heat. Add the tomatoes, season with salt and cook again for 5 minutes. For the garlic ciabatta, mix the butter with the garlic, parsley, salt and pepper well. Brush the bread slices with it and roast in the oven until golden brown. Before serving, pour the herbs over the mussels and serve immediately with the warm garlic ciabatta. Also throw away mussels that have not opened.