A few days ago I posted some pictures of a street market stand in Paris and in the foreground there was a pile of beautiful leeks — poireaux in French. That made me realize it had been a while since I had cooked and eaten leeks. Now is the season for them, so I bought some at the supermarket last week. Walt had a good idea about how we would cook them.
There are two sort of standard ways of preparing and serving leeks in French cooking. Or three, really, if you include leek and potato soup — soupe de poireaux et pommes de terre — which is delicious. The other two ways of serving leeks are as a salad — poireaux à la vinaigrette — or in a cheese sauce as a gratin — gratin de poireaux. In our case, we wanted make a gratin with leeks and ham similar to a gratin d'endives au jambon.
As it turned out, we made both the salad and the gratin. We had enough tender white sections of leeks that we could wrap four of them in ham and cook them in the cheese sauce. We also had enough shorter sections left over to make a salad. Either way, the trimmed leeks need to be either steamed or boiled first. I used a steamer. The leeks should be fork tender.
Roll each section of cooked leek in a slice of jambon de Paris ("boiled" or "Danish" ham). Make a cheese sauce. For four ham-wrapped leek sections, I made a béchamel ("white") sauce using 35 grams of butter (2½ Tbsp.) and 35 grams of flour (4 Tbsp.) — the quantities are approximate. Cook the flour in the butter for 3 or 3 minutes and then gradually add about two cups (50 milliliters) of milk or half-and-half, stirring constantly.
When the sauce has thickened and is silky smooth, stir in a good handful of grated cheese (cheddar or Swiss). Season the cheese sauce with salt, pepper, and grated nutmeg. Put some sauce in the bottom of a baking dish, lay on the wrapped leeks, and pour the cheese sauce over them. Sprinkle on a little more grated cheese if you want. Bake the dish at 180ºC (350ºF) until the sauce is bubbling and the top surface is browned. Serve hot with good bread.