Fry the onions in a large saucepan in olive oil on a medium to low heat and season with salt and pepper.
Once the onions are translucent (after around 5 minutes) add the garlic and fry for a couple of minutes.
Then add the frozen peas, soaked cashews and butter beans.
Stir together to combine before adding the stock and the fresh mint before reducing heat to a low simmer. Cook for 15 minutes.
Reserve a large spoonful of peas/onion to garnish on top of the soup. Using a hand blender, blend the soup until smooth and add the lemon juice. Add salt and paper to taste.
Top with a scattering of the peas/ onion, some reserved fresh mint and some optional flakey salt and black pepper.