Braise the onion in the butter in a soup pan (cover) until it is soft.
Add the boiling hot broth, whipped cream, peas, mint leaves, salt and pepper. Bring to the boil and then simmer for 5 to 10 minutes. The shorter, the more beautiful bright green the soup, but also the tougher the pea skins.
Puree the soup thoroughly with the hand blender. Preferably get it through the stirring sieve for a velvety soft result.