Place the onions in a large saucepan and cook with oil until they are soft.
Add the chopped broccoli, including the stalks and cook on a medium heat. Pour in a bit of chicken stock so it just covers the bottom of the pan, turn the heat right down and cover for 10-15 until the broccoli has softened.
Add your bag of watercress, spinach and rocket and stir until it has wilted.
Take off the heat and add the rest of the chicken stock. With your hand blender whizz everything up. Your mixture will be a little thick now so add the vegetable stock and blend again until smooth.
Put the soup back on the hob and heat back up to serve. I bought pre cooked salmon and sprinkled it on top of my soup cold. You can always add the salmon and stir it all in.