Make the Dough for Buns: Combine all the ingredients for the bun in the bowl of a stand mixer, or a large bowl. Mix and knead until everything comes together into a smooth dough, about 5-7 minutes with the stand mixer. Dough should be soft and pliable.
Place the dough in a greased bowl. Cover and let rise until doubled in volume, about 1 hour.
Grease a 9"x13" cake pan. Set aside.
After the first rise, gently punch the dough and divide into 12 equal pieces.
Shape each piece into a rough ball by pulling the dough into a very small knot at the bottom. Roll into a smooth ball and evenly place them in the greased pan.
Cover loosely with plastic wrap and let rise for 45-60 minutes.
About halfway through the rising, preheat the oven to 350°F.
Make the Coconut Sauce: Last 20 minutes of rising, make the sauce. Combine all the ingredients for the sauce in a small saucepan over medium-high heat. Whisk well to combine and cook for 5-7 minutes until sauce thickens.
Make Pani Popo: After the buns have risen, pour the sauce evenly over them and bake for 18-25 minutes until the tops are golden brown. I baked mine for 22 minutes.
Cool in the pan and serve them warm from right out of the pan. If you want to save them for later, then invert them onto a cooling rack, store in an airtight container for up to 2-3 days.