Blend together the mint leaves, coriander leaves and stalks, ground cumin, caster sugar, chilli and 50g of yogurt until smooth. Season with salt, then stir in 150g more yogurt and lemon juice to taste. Adjust the seasoning and serve. To blanch the vegetables, bring a large pot of salted water to the boil. Throw in each vegetable, separately. Return to the boil, then time the cooking: artichokes and mushrooms take two minutes, cauliflower and asparagus take one. Remove with a slotted spoon and plunge into cold water to stop the cooking. Squeeze mushrooms to remove any excess water. Broccoli, radicchio, fennel and peppers will not need blanching. For the marinade, place half the yogurt, the oil, lemon juice, spices, garlic, ginger and cashew nuts in a blender and blend until smooth. Stir in the remaining yogurt and season generously. Preheat the grill to its highest setting, or light the barbecue. Oil a grill rack or a large baking tray. Dip the vegetables in the marinade and coat well. Place on the rack or tray and barbecue or grill until the paste turns golden and charred in places. Turn and repeat; it takes around ten minutes in total. Baste the vegetables with butter and serve with the lemon wedges and Creamy Mint Chutney.