Bring a saucepan of water to a boil, and add the green beans. Reduce the heat and simmer 3 to 5 minutes. Drain, rinse under cold water, and pat dry. Set aside.
Melt the butter in a medium-size saucepan, and add the shallots. Sauté over medium heat for 3 minutes.
Stir in the stock, cream, and mustard, and cook until the mixture is just slightly thicken