Octopus with Mustard Greens and Rice

Name: Octopus with Mustard Greens and Rice
Ingredients: 2 kilos octopus washed but whole (if you have a chance to put it into the freezer over night it actually helps tenderise it); 1 very large onions whole but without the skin; 7 cloves of garlic, cut length ways into fat slices; a bunch of mustard greens or failing this some healthy and good radish greens (which is what I used as I couldn't find the former in that moment), thoroughly washed and picked for the best leaves; a bunch of broccoli, washed and made into smaller pieces, if you have access to broccoli rabe or cimi de rape they are better; a large bunch of parsley, washed, picked and chopped; a large bunch of cilantro, washed, picked and chopped; 300 g basmati rice; EV olive oil; salt and pepper