Put the vegetables in a large bowl, add the turmeric and toss until they are lightly coated.
Mix all the ingredients for the garam masala together in a bowl.
Heat the oil in a large, heavy-based pan over high heat, then reduce the heat. Add the vegetables and stir-fry for 2-3 minutes, or until they are light brown. Remove from the pan with a slotted spoon and set aside.
Add the bay leaves and garam masala to the pan and stir-fry for about 1 minute, or until fragrant. Add the ground ginger, onions, chilli powder, cumin and sugar and stir-fry for a further 1 minute, or until the spices change colour. Sprinkle over a few drops of water to prevent burning, if necessary. Add the vegetables, season with salt and stir thoroughly.
Add the flesh of 2 oranges, reserving the rest for the garnish. Mix well, then pour in 125ml / 4 1/2fl oz (1/2 cup) water, cover and cook over low heat for about 15 minutes.
About 5 minutes before the end of the cooking time, add the chillies. There should be very little sauce left in the pan. Garnish with the reserved orange.