This recipe is for Jules, who asked for it. It's a good use for the end of the celery, where you have the heart and maybe a couple of pale little stalks left. It's also a good use of one of those tiny little cloves of garlic that you find at the center of a soft neck garlic. In some dishes, the French want the garlic to be a subtlety, and not clobber you over the head with its flavor; they specify 'enough garlic to fit on the end of a knife', which is what you want here. Be sure to temper the egg correctly, or you'll have Cream of Leek and Celery Egg Drop Soup.
3 T butter
3 small to medium leeks, cleaned and finely sliced
the heart of celery, including the leaves, finely sliced
½ tsp sea salt
Melt butter in 3 quart saucepan on medium low heat. Add leeks, celery and salt and sweat the vegetables until they are soft, but not browned.
1 tiny clove of garlic
Mince the garlic finely and add as much as will fit on the tip of your knife. Cook it with the leeks and celery until soft (watch that it doesn't get brown). Turn down the heat and shove the vegetables to the sides of the pan.
2 T butter
2 T flour
Melt the butter and add the flour; cook the roux for a minute or two, and then mix into the vegetables.
2 cups chicken stock
white pepper, nutmeg
Stir in the stock and add a good grinding of fresh white pepper and nutmeg. Bring the heat back up to medium and cook until the vegetables are cooked through, about 10 minutes. Blend the soup until smooth with an immersion blender, or whirl in blender in batches and return to pan.
1 cup milk
Add the milk and bring to almost to a simmer. Once the milk is added, don't let it boil again.
In a bowl, beat the egg. Temper the egg by briskly whisking in two or three ladles full of hot soup, which you pour slowly into the egg. Once the egg is hot, whisk it into the soup. Let it cook until it's a little more thickened while stirring, about a minute or two. Turn off the heat, check the seasoning and serve in shallow bowls.
A nice crusty bread and butter, and a salad rounds this soup out nicely. Serves two.