Melt the butter in some olive oil in a saucepan over a medium heat.
Add the chopped onion and cook it until softened.
Add the chopped potatoes and spices. Cook for a couple of minutes.
Add the lettuce, rocket and peas and finish them off with the stock.
Bring to a gentle boil and cover.
Give it a stir and gently simmer for 20 minutes.
Purée the vegetable using a hand blender.
Adjust with salt & pepper and add the cream.
Bring it to a gentle boil and simmer for a couple of minutes