I like to serve this soup on Shavuot, the Festival commemorating the giving of the Ten Commandments, when it is traditional to eat dairy foods.
Cut the broccoli flowerets and reserve them. Scrape or trim the stems. Cut the stems into 1/2 inch slices. Par-boil about 1 cup of the smallest flowerets. Peel and cut the potatoes into 1/4 inch thick slices. Heat the butter, brown the onions and garlic, add the potatoes and broccoli. Stir until lightly brown. Add the broth, salt, and pepper, and simmer 20 minutes or until potatoes are tender. With a food processor, process the soup until smooth. Return to pot, add buttermilk, nutmeg, and peppers. Heat just until hot, serve sprinkled with flowerets and dill. Serves 8-12.