1. Fry the onion, minced, in 1 tbsp. butter until soft.
2. Add the potatoes, peeled and chopped, chicken stock, salt and pepper.
3. Cook until the potatoes are soft, then cool.
4. Sieve or liquidize the soup.
5. Add the cucumber, peeled and finely chopped and the juice of the lemons. Chill the soup.

To serve:

1. Whisk the soup.
2. Add 1 cup cream and mint leaves in each bowl, serve ice-cold.