Leeks are very tolerant of cold and, in the UK, can be harvested throughout the winter. Mounding up the soil around the leaves as they grow – which is why you should always wash leeks well - results in an increase in the prized white portion but all parts of the Leek can be eaten, including the roots. A member of the Onion (Allium) family, which includes shallots, onions, garlic, chives and ramson, it’s the inner leaves and roots of the Leek which have the strongest flavour. The dark green tops tend to be tougher and have more of a brassica-like flavour which makes them valuable for adding to soups and stews. If you’re looking for herbs to go with leeks, think of tarragon, chervil or thyme. And if the leeks you buy still have their roots, they are delicious pickled or fermented , like London Fermentary’s “Luscious Leeks”.
Members of the onion family share a strong, often pungent, sulphurous flavour when raw - garlic in particular. These are excellent qualities when it comes to deterring animals from eating the plants. Cooking transforms this chemical defence into a savoury, almost meaty quality which is valued by many cultures in in thousands of dishes. The cooking method and temperature affect the flavour balance of alliums. Cooking at high temperatures in fat produces a stronger flavour while baking and drying generate trisulfides which have the characteristic notes of overcooked cabbage, and pickling results in relatively mild flavours.
Nigel Slater describes the Leek as “the onion’s refined sister” … “for the times you want the latter’s silken texture but less of its bold sweetness”. Leeks cook best in butter. Sliced thinly and cooked until soft and lustrous, they are delicious added to a bowl of steamed mussels; add a little cream to leeks cooked in butter and you have the filling for Flamiche, or Flemish Leek Pie, which is encased in puff pastry; chicken and leeks make a very good marriage as a creamy filling for a pie or in a brothy soup or stew; creamed leeks partner beautifully with smoked haddock, top off with mashed potato. You can briefly boil whole small leeks until tender, drain them and top with a dressing of shallots, vinegar and oil with cornichon and chopped hard boiled eggs and you have Leeks Gribiche.
Leeks love cheese you can serve them gratineed – boil the leeks for 3-4 minutes until just tender, drain well, place in a shallow buttered dish, make a cheese sauce and pour over, top with a little more grated cheese and bake in a hot oven for 30 minutes. There’s Leek and Potato soup, of course, or a Scottish cock-a-leekie soup, both perfect winter warmers. In Rosie Syke’s book, The Sunday Night Book, there is a delicious take on Welsh Rarebit using leeks and Caerphilly cheese. Check out our next Monthly Report, which will be out on 6 December, for how to make it.