Moules-Frites

Moules-frites is a pot of mussels steamed open in white wine, butter, celery and onion, served alongside a cone of double-fried chips and a bowl of mayonnaise. It isn't really one recipe so much as a national arrangement: order it in a fisherman's café in Ostend or a starched-tablecloth brasserie on Brussels' Rue des Bouchers, and what changes is the broth, never the pairing.

What it really is

Live mussels go into a hot pot with celery, onion and a splash of white wine, lid on, for a few minutes, until every shell pops open; butter or cream finishes the sauce at the end. Moules marinière — wine, shallot, parsley — is the base version served across the border in France, but nature, à la crème, à la bière blanche and even au roquefort are all standard menu variants in Belgium, and none of them ever displaces the other half of the plate. The chips are fried twice, low first to cook the potato through, then hot and fast for the crust — the technique Belgians will tell you, correctly, that France later adopted.

How it's served

• In the black iron pot the mussels cooked in, its lid nearby for discarding the empty shells.
• Chips in their own paper cone or bowl, mayonnaise alongside, never poured over the mussels.
• With a wedge of bread for the broth, and a Belgian white beer to drink.

How to write it on the menu

• Name the broth style — marinière, provençale, à la crème, à la bière — it's the one detail regulars actually choose the dish by.
• List the chips and mayonnaise as part of the dish, not a side ordered separately; the plate is judged as one thing.
• Flag the shellfish plainly and the egg in the mayonnaise — this is one dish built around two major allergens at once, not one hidden inside the other.