Set a frying pan over a high heat. Top and tail the beans. Add to the hot pan with a pinch of salt. Fry, turning a few times, till lightly charred all over. Add to the salad.
Peel the bananas. Add to a blender or food processor with the zest and juice of the limes, 2 tbsp water and 2 tsp of the garam masala. Blend till smooth. Add a few splashes of water if needed.
Dollop the dressing over the salad. Put the frying pan over a medium to low heat. Add a handful of cashews and a pinch of salt. Toast till just golden. Sprinkle over the salad for a crunchy finish.
Slice the base from the lettuce. Separate the leaves into a bowl. Use a veg peeler to peel the cucumber. Thinly slice the cucumber. Add with the peel to the lettuce.