Start by cooking the beans according to the packet instructions ( I will tell you a secret - 50% of the time I use canned beans for this recipe as it is supposed to be a quick recipe. At times it happens that I have kept aside on purpose some beans cooked for a cassoulet or a beans soup.
Chop the cooked beetroots and set aside. I normally buy the ones that are baked and are slightly marinated in vinegar or I just bake my own and add tiny little balsamic vinegar to the whole thing.
Wash peel and chop the onion and the leek. Peel, crush and chop the garlic.
Heat the olive oil in a skillet using medium heat and when this is hot (not fuming please) put in the chopped onion and the leek and sauté until they become slightly translucent, I would say 2-3 minutes not longer. Add the rosemary spring and allow it to infuse for about 1-2 minutes and then remove.
Add in the cooked butter beans, garlic, and vegetable stock. Cover and reduce heat to low, simmer for about 7-10 minutes until the liquid reduces considerably.
When beans are done with the cooking, turn the heat off and set aside for a good few minutes to cool slightly.
When beans have cooled a little, transfer them together with the roughly chopped beets, salt and pepper to a food processor and blend until they smushed but not become a totally smooth paste.
Spoon beans into your desired dish and serve. I do prefer this cold as a spread but I do sometimes have it with a steak and mushrooms - see suggestion in recipe notes.