Warm the water. Take flour in a large bowl. Place sugar and citric acid in a cup. Place soda bicarb in another cup. Pour a little of the water over each. Pour remaining water in gram flour, add chilli and ginger. Mix well with palm till smooth.
Place the pressure cooker on gas with 1 litre water and stand.
Grease a round cooker or cake tin and place in the cooker. Allow to heat. Add sugar solution and colour to batter. Mix well till light and fluffy. Add soda solution and mix well. Pour into prepared tin before the foam goes down. Do not touch spoon now. Cover tin with a perforated lid and close cooker.
Cook without whistle for 13-14 minutes. Remove tin and allow it to cool. Cut in cubes and remove with spatula. Heat oil in a small pan. Add mustard seed, allow to splutter. Pour over dhokla cubes. Sprinkle coconuts and coriander. Transfer to serving dish. Serve hot or cold with green chutney.