Rotkohl, Blaukrautred cabbage

Brassica oleracea var. capitata f. rubra. The same headed cabbage as the white one, but with anthocyanins in the leaves, which give it the violet.

It is braised, not boiled: with apple, onion, vinegar, clove and bay, often with a little sugar or jelly. It belongs with roast goose, duck, Sauerbraten and Rouladen.

Vorsichtwatch out

Anthocyanins work as an acid indicator. In acid they read red, in neutral or alkaline conditions they tip to blue grey.

So the vinegar or the grated apple goes in at the start, not at the end. Braise the cabbage in plain water and you get a dull blue grey side dish that tastes fine and looks wrong.

If the colour has already dropped, add a splash of vinegar or lemon juice to the hot pot. It comes back while you watch.

In Mexikoin Mexico

It is called col morada and sits in every mercado. No substitute needed, it is exactly the same cabbage.

In Mexico it usually goes in raw, in salads and on tacos. Braised, hardly anyone here knows it, though the vegetable itself is familiar.

Kaufenbuying

Take a heavy, firm head with tight outer leaves. A half head in plastic wrap has often faded already at the cut face.

The juice stains as you cut. A wooden board takes it up, a plastic board is easier to get clean.