In a small bowl, combine warm milk and instant yeast. Set aside.
In a medium mixing bowl, add all-purpose flour, sugar, and salt. Mix until combined.
Add vegetable oil.
Slowly add the yeast mixture to the dry ingredients. Use a pair of chopsticks to mix until combined. Then, use your hands to knead it into a dough.
Separate the dough into 8 equal portions. 7 of them would be kneaded into a small round dough. Separate the remaining dough into 7 equal portions, and knead into a raindrop shape.
In a small bowl, combine cacao powder and hot water.
Prepare a pan of warm water. Place your bamboo steamers on it. Place the dough in the steamer.
Brush a single layer of chocolate sauce onto the round dough. Cover with lid and let it rise for 1 hour or 1.5x bigger than its original size.
The dough is done rising once the mushroom "skin" is formed and cracked.
Steam it for 20 minutes on medium-high heat. Turn off the heat and let it sit for 5 minutes. Do not open the lid in between.
Enjoy them with sweetened condensed milk.