Broccoli-Cheese Soup

From America's Test Kitchen Season 12: Soup and Bread from Scratch

We were after a soup with pure broccoli flavor that wasn’t hiding behind the cream or the cheese. Overcooked broccoli has a sulfurous flavor, but we discovered when we cooked our broccoli beyond the point of just overcooked—for a full hour—those sulfur-containing compounds broke down, leaving behind intense, nutty broccoli. Its texture was fairly soft, but that was perfect for use in a soup. Adding baking soda to the pot sped up the process, shortening the broccoli’s cooking time to a mere 20 minutes. A little spinach lent bright green color to the soup without taking over the flavor. After adding cheddar and Parmesan, we had a soup so full of flavor and richness that it didn’t even need the cream.