Place the baking powder and fine granulated sugar for the batter in a large mixing bowl.
Stir through the water and milk, then mix this mixture into the baking powder and sugar mixture. Gradually mix in the all-purpose flour for a soft dough. Let the dough stand in a warm place for about 1 hour.
For the filling, remove the skin from the mango and cut the flesh from the pit. Cut the pulp into coarse pieces and set aside for the sauce.
Cut off the lychees and add them together with the ground almond kernels and half of the chopped mango. Stand for 20 minutes.
In the meantime, cook the sauce. Blend the mango set aside and the orange juice in a hand blender. Press the mixture through a sieve with the back of a spoon for a smooth sauce.
Divide the dough into 16 equal parts. Roll out each part on a lightly floured surface into 7, 5 cm round disks.
Spoon a tiny bit of the mango and lychee filling onto the center of each round disk and fold the dough over the filling to form a semicircle. Press the edges together firmly to seal the wrappers.
Place the dumplings on a heatproof plate in a steamer, cover and steam for about 20 to 25 min until cooked through.
Remove the mango dumplings from the steamer, dust with a tiny bit of ground cinnamon and bring to the table with the mango sauce.