In a saucepan, bring water and sugar to a boil, then pour half of it into the glutinous rice flour. Stir until the dough is smooth but not sticky, and let it rest for 15 minutes. This helps the dough achieve the perfect chewy texture.
Scoop about 1 ounce of dough and roll it into a smooth ball. Using your thumb, create an indentation in the center for the filling. Make sure there are no cracks, so the ube doesn’t leak while frying.
Add a small scoop of ube halaya into the indentation and pinch the edges to seal. Roll again until smooth, ensuring the filling is completely enclosed.
Lightly dip the dough balls in water, then roll them in sesame seeds to cover completely. Repeat for all dough balls. This adds a crunchy, nutty layer that makes every bite irresistible.
Heat oil to 325°F and fry the buchi in medium to low heat. Move the balls gently to avoid burning, and cook until they float and turn golden, about 5–7 minutes. Transfer to a wire rack to drain excess oil.