Step 1

Coat an 8x8-inch square baking dish with coconut oil. Trim 1 fresh banana leaf, if using, to cover the bottom of the baking dish and line the baking dish with the leaf. Rinse 2 cups glutinous rice in a fine-mesh strainer until the water runs clear.

Step 2

Transfer the rice to a small pot or Dutch oven. If using pandan leaves, wrap 2 tablespoons in a cheesecloth and tie with kitchen twine to form a sachet. Add the sachet, 1 cup of the coconut milk, 1 cup water, and 1/4 teaspoon of the kosher salt to the pot and stir to combine. Bring to a boil over medium heat.

Step 3

Reduce the heat to low. Cover and simmer undisturbed until all the liquid has been absorbed and rice is slightly undercooked, about 25 minutes. Meanwhile, arrange a rack in the middle of the oven and heat the oven to 375ºF. Make the coconut caramel.

Step 4

Place the remaining 2 cups coconut milk, 1/2 cup packed dark brown sugar, 1/2 cup packed light brown sugar, and 1/4 teaspoon of the kosher salt in a large saucepan and bring to boil over medium-high heat, stirring occasionally. Reduce the heat to maintain a simmer and cook, stirring occasionally, until the mixture thickly coats the back of a spoon and you can see the bottom of the pan while stirring, about 35 minutes. Stir in the remaining 1/4 teaspoon kosher salt. Remove 2/3 cup of the coconut caramel and reserve for the top.

Step 5

Stir the cooked rice into the pot with the remaining caramel and stir until there are no white streaks and the rice is completely coated. Transfer into the baking dish and smooth the top. Pour the reserved 2/3 caramel sauce over the rice and smooth the top.

Step 6

Bake until the top is bubbly in the center and the caramel on top has thickened slightly, 30 to 35 minutes. Let cool 30 minutes before serving. Slice the biko into squares and serve. Discard the banana leaf, if using.