From my local supermarket; can't take onions anymore, they give me heartburn...
Leeks, sometimes called "the gourmet's onion" are related to onions and garlic, but have flat leaves instead of tubular and relatively little bulb development. They're easy to grow and delicious, with a taste all their own, very much like a mild onion. The thick leaf bases and slightly developed bulb look like a giant green onion, and are eaten as a cooked vegetable.
Today leeks are grown as an excellent substitute for onions and for its own unique mild onion flavor in soups and other dishes.
Generally only the white part of leeks are consumed. To prepare leeks for cooking, trim the roots, cut off the tops just where white is turning to pale green, and remove the toughest outer layer of leaves. Careful cleaning is necessary so you don't end up with "gritty" leeks since dirt can easily get in between the leaves when the plant is growing. Cut the leek in half lengthwise and rinse the pieces thoroughly under running water, first holding one end and then the other to wash all the leaf surfaces briefly to get rid of any trapped soil.
Leeks can be poached, steamed or braised whole, or chopped crosswise for use in sauces, vegetable dishes, soups, casseroles and stir-fries. Combined with potatoes, they're the key ingredients in the classic recipe vichyssoise, or leek and potato soup. Here's one version:
Vichyssoise
3 large potatoes, peeled and diced
4 cups chicken stock
2 large leeks, thoroughly washed and sliced
4 tbsp butter
½ to 1 cup light cream
salt
white pepper
fresh chives for garnish
Cook potatoes in chicken stock until tender. Sauté leeks in butter over medium-low heat until soft. Add leeks to potatoes and stock and puree in a blender. Stir in the cream and season with salt and pepper to taste. Serve very hot (but don't boil) or extremely cold. Garnish with chives.