This is a very delicious Cream of Broccoli Soup that I make when I have a big bag of broccoli stalks in the freezer. It's modified from an epicurious.com recipe.
In a heavy saucepan, saute 3/4 cup of chopped onion & 1 carrot, sliced thinly with 2 tsp brown mustard seeds and 2 tbsp butter over moderate heat.
When onion is soft, add 3.5 cups chopped broccoli, 4 cups broth and simmer 15-20 minutes, until broccoli is very tender.
Puree in batches until smooth and transfer to a second pot. Reheat (but don't boil) soup and whisk in 1.5 tsp of lemon juice, season and stir in 1/4 cup of heavy cream (or homogenized milk). Serve.