I didn’t understand leeks when I was growing up; in fact, I never ate them. It took living in France for me to fall for them. This Leek Quiche recipe, from my cookbook “V Is for Vegetables,” was not only the first thing I learned in cooking school in Paris; it was also part of my final “exam.” I had to make it under the close scrutiny of the chefs. So you’d better believe I take leeks seriously. Leeks are the mildest of the indispensable onion family, less pungent than garlic and shallots, richer and more discreet when cooked. We do not eat them raw, but they soften quickly, and as they warm, their deliciousness is revealed. Leeks are easy to use. Make sure to wash them thoroughly (soil lodges in their tight layers). This quiche has three distinctive components: the dough, the filling and the egg mixture, good things to perfect! It's delicious for breakfast and lunch at home with any number of filling variations: mushrooms, spinach, onions and so on.…