Step 1In a dry frying pan heated over low heat, toast the sesame seeds until fragrant, 1 to 2 minutes. Remove from heat and crush the sesame seeds to a coarse powder using a spice grinder or mortar and pestle. Set aside.
Step 2In the dry frying pan, toast the flour in the same way, until it tastes cooked and smells toasty, 2 to 4 minutes. Remove from heat.
Step 3In a bowl, combine the crushed sesame seeds, flour and sugar, mixing well.
Step 4Melt the lard or coconut oil, then stir it into the sesame seed mixture. Set aside to cool, then refrigerate until set.
Step 5Roll the set stuffing into balls the size of grapes (about 1½ teaspoons filling, or 8 grams, each) and dust using glutinous flour to prevent sticking; you should have 24 balls. Freeze the formed fillings to harden.
Step 6Place the glutinous rice flour in a large bowl. Add the cooking oil and enough water to make a putty-like dough. The dough should not stick to your fingers. Break the dough into balls a little larger than the stuffing balls (a scant 1½ tablespoons, or 14 grams), dusting the work surface with rice flour as necessary.
Step 7Press your thumb into the center of each ball to make a cup. Press a frozen stuffing ball into each cup and draw the dough around it to enclose it completely.
Step 8Bring a pot of water to a boil. Add several rice balls and gently simmer until they begin to float, about 3 minutes. Repeat until all of the balls are cooked. Serve 4 balls per person in a bowl of the hot cooking water, sprinkling over a few osmanthus blossoms to garnish, if desired.