Cauliflower and broccoli are essentially interchangeable, though you might not think so until you saw a broccoflower or Romanesco broccoli; the appearance of each makes the link clear. Broccoli cooks a little faster, and the trimming and cleaning techniques are a little different (I think it’s worth it to peel the stems of broccoli; cauliflower has no stems to speak of), but almost every recipe for one can be used for the other. Cauliflower’s white color and slightly richer but milder flavor make it, I believe, a little more versatile.