In a large skillet, add the trimmed green beans with approximately 3 cups of water. Over medium heat, bring to a simmer and steam the beans for 5 minutes. They will be bright green and slightly tender. Remove beans from skillet and transfer to a bowl and cover to keep warm. Drain water from skillet.
In same large skillet, add 2 tablespoons of butter and saute the mushrooms for approximately 5 minutes, Add the shallots and saute for 2 more minutes. Add sherry and saute for 2 more minutes, until evaporated.