Warming tangyuan in spicy ginger soup is a soothing winter dessert. A family recipe with fresh ginger flavor and comforting heat.
Toast black sesame seeds over medium heat in a dry skillet, stirring constantly for 2-3 minutes until fragrant. Let cool, then grind into a fine powder.
Combine ground sesame, confectioners' sugar, and melted butter in a bowl. Mix well, chill for 15 minutes, then roll into small 1/2-inch balls and freeze until firm.
Mix sweet rice flour with water, knead until a smooth, soft dough forms. Cover with a damp towel to prevent drying out.
Divide dough into 1-tbsp pieces, flatten each, wrap around a frozen sesame filling, and pinch to seal. Roll gently to form smooth balls.
For the soup, slice ginger and add to 4 cups water in a saucepan. Bring to a boil, then reduce to a simmer for 10 minutes. Add rock sugar and salt; stir until dissolved.
Bring a separate medium pot of water to a rolling boil. Add tangyuan balls, stir gently to prevent sticking. Cook over medium-high heat until they float plus 3 minutes.
Transfer tangyuan into serving bowls. Ladle hot ginger syrup soup over the tangyuan, and serve immediately for best texture.