Put a splash of oil in a frying pan over medium-high heat and add the bacon pieces. Cook until browned, stirring frequently, 4-5 mins. Add the shallot and cook until softened, another 3 mins. Add the green beans and a splash of water. Cover the pan with a lid (or some foil) and steam until the beans are tender, 4-5 mins. Transfer to a bowl and cover with foil to keep warm. Wipe the pan out as we will need it for the sauce.