For the dressing
Cook the vegetables separately in a saucepan of salted boiling water for 4–5 minutes. Drain well and chill.
To make the dressing, heat the oil in a frying pan and fry the peanuts, tossing frequently, for 3–4 minutes. Remove from the pan with a slotted spoon, and drain on kitchen paper. Chop the peanuts in a blender or food processor, or crush with a rolling pin, until fine but not ground to a powder – leave a little texture.
Pour all but 1 tablespoon of the oil from the pan, and fry the garlic and onion for 1 minute. Add the chilli powder, sugar, a pinch of salt and 450ml/3⁄4pt water, and bring to the boil.Stir in the peanuts, reduce the heat and simmer for 4–5 minutes until the sauce thickens. Add the lemon juice and set aside to cool.
Arrange the cold vegetables in a serving dish, and put the peanut dressing in a small bowl in the centre. Serve.