In a large pan, combine the frozen peas, vegetable stock, granulated sugar, mint, salt, and pepper.
Bring the mixture to a boil, then reduce the heat, cover, and simmer for 15 minutes.
Remove and discard the mint.
Purée the pea mixture in a blender or food processor.
Return the purée to the heat.
In a bowl, blend the egg yolk with half of the single cream.
Stir this mixture into the soup.
Return the soup to a clean pan and reheat, ensuring it does not boil.
Taste and adjust the seasoning if necessary.
Serve the creamy pea and mint soup garnished with the remaining single cream.