1) Put the rice flour into a large bowl. Bring the water to a boil and add the brown sugar, stirring to dissolve.
2) Pour the sugar water over the rice flour and stir together with a wooden spoon to combine. You can add up to 1/3 cup more water if the mixture seems dry and isn't coming together. Once the dough is cool enough to touch with your bare hands you can stop using the spoon and just knead the dough - don't overwork it or it will become tough.
3) Once the dough is soft and smooth, break off a piece about the size of a golf ball and roll between your hands to form a ball. Place in a dish and cover with some plastic wrap, then repeat with the remaining dough.
4) Take one of the dough balls and make a well in it with your thumb. Place a teaspoon of the red bean paste in the well, then push the dough together to cover up the filling.
5) Roll the ball between your hands again to make it smooth and round without cracks.
6) Wet your hands with water and roll the dough ball in a dish of the sesame seeds, pressing gently to get the seed to adhere to the dough ball. Place the ball back under the plastic wrap and repeat with remaining balls.
7) Pour the oil in a wok or other pan so it is deep enough to cover the dough balls when you fry them. Heat over medium heat.
8) Once the oil is hot enough, place a few dough balls (about 4-5) in the hot oil and let cook. Use a ladle or wooden spoon to press the dough balls against the side of the pan to rotate them - this is important to help them cook evenly and prevent spots from burning.
9) When the seeds start turning golden and the dough balls start floating to the top of the oil, the balls should be done - about 5 to 6 minutes.
10) Remove the balls and drain them on paper towels, then repeat with the rest.