First, if you decide to use dry borlotti beans you will need to soak them overnight and cook them for 1 hour at least. If you are using canned ones you can of course skip this.
In a mixer put the canned borlotti beans together with the water. If you used dry beans add some of the cooking water.
Add garlic, salt & black pepper and some olive oil
Mix until you get a nice mixture. It should be not too thick, so in case of that you can add some water.
Transfer the mixture to a pan and add the fresh rosemary. Turn on the heat on low and cover the pan.
Meanwhile lets cook the mushrooms. After you cleaned them, finely chopp the white part of the green onion and put them in a pan with a drizzle of olive oil. Cook them for about 10 minutes on a medium heat.
Now back to the soup. After 10 minutes the soup should be more thick and the rosemary should have release its flavour.
Transfer the soup and the mushrooms in a bowl and serve it with the remaining part of the green onion and some olive oil in top.