Slice sponge cake, spread on platter or custard dish, set aside.
Place water, milk, butter and sugar in a one-quart saucepan. Bring to a boil. Add well-beaten eggs, vanilla and cinnamon. Again, bring to a boil, stirring constantly.
Mix ⅓ cup water with cornstarch until smooth. Pour into milk mixture until thicken.
Remove from heat, and spread over Sponge cake.
Sprinkle cinnamon over latiya. May be serve like custard.