Rinse your sesame seeds in a very fine mesh strainer and then toast in a skillet over medium heat until they begin to pop. In a food processor, add the toasted sesame seeds and sugars. Process until fully combined and the seeds have reached the consistency of sugar (do not overprocess to a paste).
Stir the sweet potato together with the sweet rice flour and sugar until fully combined. Add more rice flour, a tablespoon at a time if the dough seems unmanageable sticky. You can add additional sweetener to compensate for any added starch to taste.
Start preheating a lightly greased pan over medium heat. Scoop out slightly mounded tablespoons of dough at a time and flatten in your palm. Fill with ½ teaspoon of black sesame sugar and gently fold the edges of the pancake over the mound of sesame sugar. This can be a finicky process; I’ve found wetting my hands with a little water helps keep the dough from sticking quite as much.
Press a few sesame seeds on top (this is purely for aesthetic purposes).
Nudge the tablespoon of dough directly from your palm into the pan. These are so delicate that I found I had to cook them as I made them; there can be no transferring of the pancakes from your palm to anywhere else lest you tear them.
Cook for a few minutes on each side until golden. Eat warm!