Leeks and alliums, flavouring profile

Leeks and alliums, flavouring profile

Cooked slowly, leeks and onions turn sweet and soft; raw or charred, they turn sharp and sulphurous, and the wine has to suit whichever of the two is on the plate.

The compounds that matter. Sulphur compounds, the source of the sting in a raw onion, which soften and sweeten with long cooking. Sugars released as leeks and onions sweat in butter, which make a lean, sharp wine taste thin. A green, grassy note in leek tops, which suits a white with its own green or herbal edge.

What it demands of a wine. For slow cooked leeks in butter or cream, a white with some texture and moderate acidity. For raw shallot, leeks vinaigrette or charred spring onions, higher acidity and a clean style, since a wine with its own struck match smell compounds the sulphur. Tannin and heavy oak help nowhere.

Seek. Riesling from Alsace in its dry style, the classic partner to a leek tart. Silvaner from Franken, dry, earthy and quietly herbal, which matches the vegetable's own character. Godello from Valdeorras, textured but fresh, for leeks braised in butter. Chasselas from the Valais, soft and low in alcohol, for onion tart and gratins.

Avoid

Heavily reductive whites with a smoky, struck match smell, which stack on the sulphur of the alliums. Big, tannic reds, whose grip turns bitter against charred onion. Very sweet wines, except with onion marmalade.

Three to reach for. Dry Riesling, Alsace, France. Dry Silvaner, Franken, Germany. Godello, Valdeorras, Spain.