Place the grapefruit on the chopping board and cut a third off the end. Squeeze the juice of this third into a small bowl to get around 4 tablespoons of juice. Add the lime juice and keep to one side.
Peel the other two-third of the grapefruit, cut s the flesh into segments, and place in a large mixing bowl.
Add the cabbage, carrots, lettuce, and all but a handful of the basil leaves and mix. Mix it again after adding the salk into it and set set aside while you make the dressing.
Pound the garlic, chilies, and sugar into a paste using a pestle and mortar. Add the soy sauce and muddle, then add the grapefruit and lime juice and mix again.
Tip: If your pestle and motor is large enough, add the oil and mix. If not, decant the dressing to a bowl, then add oil and whisk to combine.
Pour the dressing over the salad, mix well, then tip on to a platter or into a salad bowl.
Finally, top with the remaining basil leaves, the chopped cashews, and the crispy fried onions, and serve immediately.