Rinse and drain the dried grass jelly. Place it in a deep, heatproof container (such as a 1 1/2 cup/350ml mold). Add 1 cup (250ml) water. Put the container in a pressure cooker and steam with water for 10 minutes under pressure. Turn off the heat and let the pressure release naturally.

Open the lid and strain the liquid into another deep pot. Add the agar powder and baking soda, stirring to dissolve. Heat over low heat, stirring constantly, until it comes to a boil. Because baking soda can cause it to foam up, be sure to use low heat! After it boils, cook for about 1 more minute, then turn off the heat and pour into your preferred serving dish. Refrigerate until set.

While waiting, make the syrup. In a small saucepan, combine the sugar and 1 tablespoon (15ml) water. Heat and stir until the sugar dissolves and the mixture thickens slightly. Remove from heat and let cool.

To serve, pour the syrup from step 3 over the grass jelly from step 2, and sprinkle with the chopped raisins.