This simple side only takes five ingredients, but it's got plenty of flavor.
Prepare an ice bath.
In a large deep skillet, bring a few inches of water to a boil. Salt the water, add the green beans, and cook until crisp-tender, 3 to 4 minutes. Using a slotted spoon, transfer the green beans to the ice bath to cool. Drain the green beans.
Pour the water out of the skillet. Add the butter to the skillet. Heat over medium-low until the butter melts. Add the shallots and cook, stirring occasionally, until very tender and lightly caramelized, about 15 minutes. Add the stock and green beans. Turn off the heat and cover until ready to serve. If needed, reheat the green beans over medium-low until heated through, about 5 minutes.