Heat the oil in a wok or heavy bottomed, wide frying pan until the surface looks as though it’s shimmering.
When the oil is at this stage (hot but not smoking), add the beans, shallots, garlic and ginger and a pinch of salt and stir fry, stirring regularly until the beans are beginning to soften but are still bright green (about 6 minutes). Add the cashew nuts and fry for another minute.
Finally, make a space at the base of the pan and add the peanut butter, stir until it softens and stir to coat the beans. Pour in the soy sauce and lemon, add the chilli and stir for another minute.