This is a Julia Child classic, which I made in Paris in 1969. My first Julia Child cookbook, an English edition that Carolyn had sent me, was my original guide.
That year, just after getting married, we rented a tiny apartment on Rue de la Collegiale, just around the corner from the Rue Mouffetard, a winding street, lined with shops and stalls filled with wondrous vegetables, meats, oysters, and much more. I don't think we had a refrigerator (if we did it was miniscule) so daily shopping was a must. I was working on becoming as French as I could--studying French, reading Proust, Victor Hugo, Roger Martin du Gard's Les Thibauts, lots of Simone de Beauvoir, so it goes without saying that I tried to cook and shop as much like a French person as possible.
This was probably my first encounter with leeks. It was surprisingly thrilling to always find dark earth embedded between the layers of those fleshy green stalks).
This recipe, unlike many others of that era, is almost embarrassing in its simplicity—no beans to soak, no vegetables to sauté-- just some peeling, and chopping and into the pot!
That summer, as we traveled through France, eating lunch in tiny village restaurants, the soup that was regularly served, was surely a variation on this basic dish. I made it for years. Why did I stop? Perhaps I always thought of it as a wintry soup, not suited for southern California. I never had much interest in the cold--vichyssoise variation. As you are both living in chillier zones, you should be eating it regularly.
Here's my variation on the basic recipe, but the possibilities are limitless:
Simmer 3-4 cups peeled, sliced or diced potatoes, 3 cups thinly sliced leeks and maybe ½ cup chopped carrots in two quarts of water with 1 tbsp. salt for forty to fifty minutes (you can also use good home-made vegetable broth or chicken broth if you have it). When vegetables are fully cooked mash with a fork, or put through food mill, or do a few whirls with an immersion blender. Add salt and pepper. Just before serving, stir in a few tablespoons softened butter and add a good sprinkling of parsley or chives.