1 cup coconut milk
2 pinches of salt
1 tablespoon sugar
3 tablespoons water
1 1/2 teaspoons cornstarch dissolved in 2 teaspoons water
3 cups water
1/4 cup sweet rice, rinsed and drained, or small tapioca pearls (about 1/8 inch in diameter)
3 ears of corn, or 1 (16-ounce) bag frozen sweet corn
1/3 cup coconut milk
5 tablespoons sugar
1/2 teaspoon salt
3 large or 5 medium pandan leaves, rinsed and tied into a knot, optional (see the photo below)
1/2 teaspoon vanilla extract
To make the coconut sauce, combine the coconut milk, salt, sugar, and water in a small saucepan. Place over medium heat and bring to a near-simmer, lowering the heat if the coconut milk spits or pops. Give the cornstarch mixture a good stir and add it to the sauce, mixing well. Cook, stirring, for about 30 seconds, or until the sauce thickens; then remove from the heat.
Let the sauce cool, uncovered, to concentrate the flavors before serving. It will keep in a tightly closed container in the refrigerator for up to 3 days. Before using, reheat gently over low heat.
For the corn soup, put the water in a saucepan and it to a boil over high heat. Add the rice, stirring to prevent them from sticking together. Boil, stirring occasionally, for about 5 minutes, or until the rice is nearly cooked. If using the tapioca pearls, it will take 12 to 14 minutes for them to turn halfway clear; look for a tiny white dot in the center of each pearl. The water will seem slightly thick and viscous.
Meanwhile, if you are using, cut the kernels off the cob. If you are using frozen corn, thaw it for about 20 minutes. You should have 3 generous cups. Regardless of the corn used, use a processor to render it into a coarse texture.
When the rice (or tapioca pearl) is ready, add the coconut milk, sugar, salt, and pandan, stirring to dissolve the sugar. When the mixture comes to a near boil, add the corn. Lower the heat to a simmer and cook for about 5 minutes, or until the corn is cooked and the flavors are blended. Remove from the heat and stir in the vanilla. Allow the soup to cool for about 15 minutes. The resulting sweet soup will be thickish, like Italian risotto. Taste and adjust with more sugar and salt, if necessary. (The soup may be prepared up to 2 days in advance, tightly covered, and refrigerated. Warm over low heat, adding a splash of water to thin and prevent scorching, before serving.)
To serve, ladle the soup into small bowls and top with the coconut sauce