Use the same pan & saute ginger garlic, spring onion, onion. Saut for a min or until it turns translucent. Add cabbage, carrot, yellow, red & green capsicum. Stir fry for 2 min vegetables. Add salt & sugar. Add prawns & stir fry on high heat 2 mins. Stir in the mixed sauce. Add 1 cup water & mix. Now lets prepare the corn flour slurry. Pour the corn flour slurry in the gravy. Stir continuously until the gravy thickens & turns glossy. Gravy is ready.