The vermicelles called for in this recipe are very thin French noodles, finer than Italian vermicelli. They may be found at French food markets. To serve 8:

4 or 5 leeks, white parts only, sliced
6 to 8 potatoes, sliced
1/2 c. shredded sorrel leaves
2 tbsp. butter
2 qts. water, lightly salted
3 1/2 oz. vermicelles
1 c. heavy cream

Melt the butter in a large saucepan, add the sorrel and cook gently until the sorrel wilts into a puree. Add the leeks and potatoes and pour in the salted water. Bring to a boil and simmer, covered, for 15 minutes or until half cooked. Add the vermicelles and continue cooking, uncovered, for about 2 to 3 minutes, until everything is done. Shortly before serving, stir in the cream.