Finely chop the onion, red and yellow bell peppers, and parsley. Soak them in water until crisp, then drain in a colander.

Mix the ingredients marked with ★ in a container.

Scrub the mussel shells with a metal scrubber to remove dirt, and pull off any seaweed caught in the shells using the scrubber.

In a pot, add enough water to cover the mussels, along with white wine and a pinch of salt. Bring to a boil to evaporate the alcohol.

Add the cleaned mussels to the pot, cover, and cook until the shells open.

Drain the cooking liquid from the pot. Once cooled, arrange the mussels on a plate, keeping the half with the meat attached.