Yassa: The Citrus-Onion Technique (Senegal)

Yassa is the Casamance region's contribution to the Senegalese national table — a technique of marinating chicken or fish in lime juice, massive quantities of onion, and mustard, then grilling the protein and converting the spent marinade into the sauce. It is Senegalese cooking's most direct expression of acid as the primary flavour, and one of the most elegant examples anywhere of a single preparation that performs two functions: marinade and sauce.

Chicken, jointed, marinated in the juice of many limes, white onion sliced thin in a volume of 3:1 onion to chicken by weight, Dijon mustard, neutral oil, Scotch bonnet or habanero chilli, salt, and black pepper. A minimum of 4 hours, overnight preferred — the lime acid begins to work on the surface of the chicken and the onion softens and absorbs the other flavours. The chicken is removed, patted completely dry, and grilled over charcoal or under a broiler until well-coloured on all sides. The spent marinade — including every thread of onion — is reserved. In peanut oil, the marinade is fried until the onion completely dissolves and caramelises; the lime acid cooks off, leaving only its brightness; the mustard emulsifies into the oil. The grilled chicken is returned, covered, and braised in the onion sauce with added stock or water until very tender.

• The technique of marinating protein in an acid-onion mixture, grilling it, and then converting the spent marinade into the sauce appears in Peruvian adobo, Spanish escabeche, and Filipino chicken adob
• The idea of cooking a marinade into a sauce after it has done its first job is one of the kitchen's most elegant examples of refusing to waste

Yassa served over broken white rice, the sauce pooling in the grains' cavities. Accompaniments: French baguette (a Senegalese staple from colonial influence), cold bissap hibiscus flower drink. The flavour profile: acid and caramelised onion sweetness in equilibrium; mustard providing the emulsification and a secondary warmth; chilli heat in the background. A dish of clarity.