
Peel the sweet potatoes and cut them into chunks. Place them in a pot, cover with water, and bring to a boil. After about 2 minutes, add 1 peeled plantain cut into chunks and continue boiling until both the sweet potatoes and plantain are fork-tender. Reserve 1 cup of the cooking water, then drain.



While the sweet potatoes cook, prepare the second plantain. Peel it, cut it crosswise in half, then slice each half lengthwise into long pieces. Butter the bottom and sides of a wide, flat skillet or heavy pan.



Sprinkle the brown sugar evenly over the buttered pan. Add the cinnamon, five-spice powder, and ground ginger, spreading the spices across the base so they will season the plantain layer.


Arrange the sliced plantain pieces over the spiced sugar layer in an even pattern. Keep the heat off while you prepare the batter.



Add the eggs, powdered milk, pitted dates, boiled sweet potatoes, boiled plantain, and 1 cup reserved cooking water to a blender. Blend until completely smooth and creamy.


Pour the blended mixture into a mixing bowl. Add the rice flour and stir until the batter is smooth with no dry pockets or lumps. The batter should be pourable but thick.



Pour the batter evenly over the arranged plantains. Cover the pan and cook over medium-low heat until the cake is set and a fork inserted in the center comes out clean, about 30 to 45 minutes. If your stove runs hot, place the pan over a larger pan of simmering water to create a gentle double-boiler effect.
Let the cake rest for 10 minutes before serving. For a caramelized presentation, carefully invert it onto a serving plate so the spiced plantain layer is on top.