Peel and chop the plantain. Put the pieces into a food processor and blend on high for about 30 seconds, or until pureed.
Put the rest of the ingredients in the food processor (except for the tapioca starch) and blend until completely pureed.
Add the tapioca starch to the mixture, but blend into the puree with a spatula first, until most of the starch is blended into the mixture (and not sticking all inside the processor). Blend for 1 minutes or longer, until the puree is completely uniform.
Preheat the oven to 375 F. Line two or three baking sheets with parchment paper (yield can be unpredictable, and these may need more space than you think). Take a 1/4 cup measuring cup and portion out individual flatbreads about 3 inches from each other on the parchment paper. The batter may run a bit, but it does not run when baking, so just make sure there is plenty of space between each on the parchment paper.
Bake for 10 minutes, rotating baking sheets halfway through baking. The flatbreads should puff up a bit and be golden around the edges. When cool, you can store them in the refrigerator for several days, but they freeze even better. You can take them out of the freezer, pop them in the toaster, and voila!