Combine flour and water into a ball. Boil a pot of water and add the ball to the pot. Boil for 3 minutes, then take ball out and put into an ice bath for 3 minutes.
Add prunes to a large bowl and cover with hot water, let it sit for 20 minutes.
Drain water from prunes. Add sugar and lemon juice. Blend mixture into a paste, or mash if you don't have a blender.
The Rest of The Dough
Combine sugar, flour, baking powder, and water in a large mixing bowl. Break up the starter dough from earlier and add as well. Knead this mixture until it is thoroughly combined and no longer sticky.
Roll dough a snake and cut into 1 inch sections. Roll each into a ball, then flatten it. Put a slight indent in the middle with your thumb. Add a spoonful of the plum filling. Pinch the dough around it and seal at the top. Smooth out any lumps by gently rolling in your hands. Repeat for each section of dough.
Dip each ball into a bowl of water, then roll the ball in the sesame seeds until thoroughly coated.
Heat up a pot of canola oil to 350 F. Drop the balls in and fry for 12 minutes, or until golden brown. Take the balls out and cool on a drying rack before eating.