Separate broccoli crowns into florets. Peel stalks and cut into 1/2-inch pieces.
Bring a large pot of lightly salted water to a boil. Cook broccoli until lightly softened, about 5 minutes. Drain, rinse under cold running water, and drain again.
Melt butter in a pot, add broccoli, and cook for 2 minutes. Pour in cream and cook over low heat until broccoli is soft, about 10 minutes. Season with salt, pepper, and nutmeg. Puree broccoli with an immersion blender until smooth.