Young broccoli leaves are delicious. They make an excellent substitute for collards, if you like making a mess of greens. But rather than making a bowl of greens, I'll just add chopped broccoli leaves to stir fry and soups. Steamed first, they are nice in omelets. They are far tastier and tenderer than collards. In fact, I've stopped growing collards. It's broccoli greens for our table now.
When I grow broccoli, I'll plant one area with the intention of harvesting the head and smaller florets. Another bed is destined for greens. The reason I separate the growing beds is that I pump extra manure to the bed for greens. That way the plants get giant and lush, producing lots of tender, big leaves. I find that rabbit manure makes for really nice broccoli greens.
This bed of broccoli is in the community garden area. I have another up by the house for my personal use. Both are growing well, but the one up by my house has bigger, softer leaves. I think I over did the rabbit poop in the bed.
The only thing I have to watch out for is the cabbage moth. It's little caterpillars can make a mess of the leaves, chomping holes everywhere. While the leaves are still edible, they aren't as tender when they are being attacked by caterpillars. So I take the time to watch for them.