Fill a medium saucepan halfway with water and bring it to a boil
Add the onions and let them simmer gently for 5 minutes then drain.
In a large skillet, melt the butter over medium-high heat.
Add the onions and cook for 2 minutes.
Add the peas and cook for 1 minute.
Add the flour and cook for 1 minute, with stirring.
Add the chicken broth and heavy cream gradually, mixing it in as you pour.
Add the salt, sugar, and black pepper.
Cook for 2 to 3 minutes until thickened.
Sprinkle with mint and serve.