Sprinkle the powdered gelatin into the cold water. Whisk it with a fork. Let it stand for 10 mins till the grains swell up and it starts thickening.
Place the bowl on a double boiler or in a bigger bowl half filled with hot water. Let the gelatin dissolve completely.
Remove the bowl and allow it to cool down slightly. Stir in the rose syrup and strawberries.
Cut the sponge cake into tiny cubes. Layer the cubes in a mason jar or a small glass. Pour the gelatin mixture over it and press lightly with a spoon. Let it stand for 10 mins.
Take 1 cup cold milk and dissolve the custard powder in it.
Bring the rest of the milk to a boil. Stir in sugar. Add the custard powder dissolved in milk. Stir continuously to prevent lumps. Remove from flame after 2-3 mins.
Allow it to cool slightly before pouring over the contents of the jar or glass. Refrigerate for at least 30 mins before serving.