Bring a couple inches of water to boil in a large shallow pan; salt water and cook green beans 3-4 minutes to tender-crisp. Cold-shock beans in ice water and drain well; reserve.
Heat butter in a large, deep skillet with a lid over medium heat. When butter melts and foams, add the shallots and cook gently 10-15 minutes partially covered to very tender. Add stock and heat through. Turn off heat and cool; add beans to pan.
When you are ready to serve, reheat over medium heat and toss with tongs to heat the beans through. Season with salt and pepper to taste.