Broccoli rabe...
Firstly make sure to cut the long hard stems off, remove larger old looking leaves, blanch as others have said for about 1 min, stop cooking in ice water. I then wrap in paper towels to absorb water and keep until ready to cook.
A popular dish is broccoli rabe and sausage. I use spicy itallian (use what you like) I remove from the casing (many people leave in casing and cook as chunks), brown well in a bit of olive oil when just about brown add lots of minced garlic, red pepper flakes, final addition is the broccoli rabe which I chop into more bite size pieces.(some leave as larger pieces) Don't over cook as rabe just needs to get hot! Traditionally you add pasta (orchetta) which you can cook in the broccoli rabe water. When the pasta is al dente add to sausage broccoli rabe pan adding some cooking liquid to make a bit of a sauce so not dry, toss and grate lots of parmasean cheese on top, serve.