Peel and chop the stems of the broccoli. Separate the tops into small florets. Wash thoroughly.

Cut the base of the scallions and remove any damaged leaves. Chop the scallions, including an inch of the green part.

Bring 2 quarts of water to a boil. Add 1 teaspoon salt, then the broccoli and the scallions. Cook until tender (about 6 to 10 minutes).

Keep a cup of the cooking liquid and drain the vegetables in a colander. Discard the bay leaf. Purée in a food processor. You want a smooth consistency but with a little bit of texture. Use the cooking water to smooth the purée if necessary. Stir in butter, and season with salt and pepper (ideally fresh from a pepper mill). Grate the nutmeg and mix at the last minute before serving.