Chewy tangyuan filled with rich black sesame paste are a beloved festival dessert. A family treat with nutty, sweet flavor in warm soup.
Toast the black sesame seeds in a dry skillet over medium-low heat for 3–5 minutes until fragrant, stirring constantly to prevent burning.
Let the sesame seeds cool, then grind them with granulated sugar into a fine powder using a food processor.
Add the softened butter to the ground sesame mixture and blend to form a thick, cohesive paste. Refrigerate for 20 minutes for easier handling.
In a bowl, mix glutinous rice flour with water and knead until a soft, smooth dough forms – adjust with a teaspoon of water if dry.
Divide dough into small pieces (about 20g each), flatten into discs, and wrap each around a portion of the black sesame paste, sealing tightly. Roll into smooth balls.
Bring 4 cups water and rock sugar to a gentle boil; maintain at a simmer to avoid vigorous bubbling that could break the tangyuan.
Carefully drop tangyuan into the simmering soup and cook over medium heat. Once they float, let them simmer for another 2 minutes to ensure the filling heats through.
Serve the tangyuan hot in sweet soup, ensuring none are overcooked as this can cause splitting.