Chilled Pea Soup with Parmesan Ice Cream

• 75 g butter
• 1 onion, peeled and finely sliced
• 250 ml

To make the Parmesan ice cream, heat the cream in a pan until almost boiling. Take off the heat and stir in the Parmesan. While still hot, whiz in a blender until the cheese has melted and the mixture is smooth. Pass through a fine sieve into a bowl set over a bowl of iced water. Using a hand-held stick blender or a hand-held electric whisk, mix on low speed. It will thicken as it cools. Keep w