Heat the olive oil and butter in a heavy based pan. When foaming, add the potato. Gently fry without colouring for about 5 mins. Stir in the stock, bring to the boil and simmer for 10 mins or until the potato is tender.

Stir in the peas, bring to the boil again, then cook for about 3 mins until they are just done. Remove the pan from the heat, add the mint leaves and whizz in a blender or food processor until smooth.

To make the parmesan biscuits, heat the grill to high. Line a baking sheet with baking parchment and divide the grated parmesan into 6 long strips. Grill for 1 min or until the cheese has melted and is lightly golden. While still warm and a bit flexible, release the biscuits from the baking parchment with a palette or cutlery knife, then cool until firm.

To serve, heat the soup and divide between 6 bowls. Scatter with mint leaves and finely sliced chives, and serve with the parmesan biscuits on the side.