Brush the mussels under cold running water. Soak in cold water until the water remains clear. Peel the onions and garlic cloves and cut into strips. Cut leeks in half lengthwise and remove dark green. Rinse leeks and cut diagonally into narrow strips.
In a wide saucepan, heat the olive oil. Sauté the leek, onion and garlic strips in it. Add white wine and one eighth of a liter of water and let it boil. Rinse the chili pepper and add it to the saucepan together with bay leaves, peppercorns and a pinch of salt. Add the mussels to the boiling liquid form and cook with the lid closed over medium heat for 5 to 7 minutes.
Rinse the parsley, toss dry and chop the leaves finely. Discard any mussels that did not open during cooking. Divide the opened mussels evenly among four deep plates. Stir wine broth with parsley and pour into the plate next to the mussels.