Bring a saucepan of water to a boil. Add the peas, and simmer until crisp-tender, 3 to 5 minutes. Drain, rinse under cold water, and drain again. Set the peas aside.
Melt the butter in a saucepan, and sauté the onion over medium-low heat until soft but not browned, about 5 minutes.
Add the stock and cream, raise the heat to medium, and cook until redu