Chana chaat (mixed bean salad)

Name: Chana chaat (mixed bean salad)
Cuisine: Asian, Indian
Ingredients: 1 large handful fresh mint; ½ green chilli, deseeded; ½ onion, chopped; 250g low-fat natural yogurt; pinch salt; pinch chilli powder; freshly ground black pepper; 2 x 400g tins chickpeas, drained and rinsed; 400g tin new potatoes, drained and quartered; 220g tin red kidney beans, drained and rinsed; 220g tin black-eyed beans, drained and rinsed; 5 tbsp tinned sweetcorn, drained; ½ tsp chilli powder or to taste; 1 green chilli, finely chopped; ½ tsp chaat masala; 1 tsp lemon juice; 1 small onion, finely chopped; 1 tomato, finely chopped; 1 tsp garam masala powder