I noticed today my purple sprouting broccoli is growing pods where leaves should be. Why is this? What can/should I do about it?
What you have here are seed pods - your broccoli has started to go to seed.
The plant is approaching the end of its lifecycle, when it developes seeds for a new generation and dies. The leaves are no longer needed for photosynthesis and the plant discards them. The process can be sped up if the environmental conditions are “difficult” and the plant decides to set seed prematurely: If the plant is stressed, it will try to at least produce seeds before it kicks the bucket.
This is probably not what you want, but there’s nothing you can do about it now. For the future, evaluate why your broccoli bolted. Was it too crowded? Too dry? Too hot? Lacking fertilizer? Did you forget to harvest (= cutting the flowers, which can’t go to seed, encouraging the plant to grow new flowers) in time? This should help you to get better results next time.