Prick the sweet potato in five or six places with a sharp knife. Place it on a microwave-safe plate and microwave it on HIGH for 5 minutes, rotating it halfway through. Check to see if it’s fork-tender, and continue microwaving in 1-minute increments until it is. Let it cool enough to handle, then cut it in half, scoop out the flesh into a small bowl and mash. Add ¼ cup (60 milliliters) of the coconut milk and stir until combined. Cover and refrigerate until cold, 2 hours.

Position a rack in the middle of the oven and preheat to 400 degrees. Line a large, rimmed baking sheet with parchment paper. Lightly flour your work surface.

In a large bowl, whisk together the flour, baking powder, brown sugar, cinnamon, nutmeg and salt. Add the chilled sweet potato-coconut milk mixture and mix just until the dough comes together. If the dough is not holding together, add more coconut milk, 1 tablespoon at a time, until it does. Turn the dough out onto the floured surface, flour your hands, and press the dough together with the heel of your hands. Pat the dough into a rectangle about 1-inch thick.

Using a 2-inch biscuit cutter, cut the dough into rounds. Place the rounds about 1 inch apart on the prepared baking sheet. Lightly brush the tops of the biscuits with the remaining ¼ cup (60 milliliters) of coconut milk.

Bake for 12 to 15 minutes, until the biscuits are puffed and the bottoms are golden brown. Transfer to a wire rack. Serve warm or at room temperature.