Prepare the Dough Mix warm milk, water, yeast, and 1 tbsp sugar in a small bowl. Let it sit 5–10 minutes until frothy. In a large bowl, combine flour, remaining sugar, and salt. Add the yeast mixture and oil, then knead 8–10 minutes until smooth. Cover and let rise 1–2 hours until doubled.
Prepare the Filling Heat sesame oil in a pan and sauté garlic until fragrant. Add diced pork and cook until browned. Stir in soy sauce, hoisin, oyster sauce, and sugar. Simmer 5–7 minutes until tender. Add green onions and let the mixture cool.
Assemble the Manapua Punch down the dough and divide it into 12–15 portions. Flatten each portion into a circle. Place 1–2 tbsp of filling in the center, gather the edges, and pinch to seal. Shape into smooth buns.
Cook the Manapua Steaming: Place buns on parchment in a steamer and steam for 12–15 minutes.
Baking (Optional): Preheat oven to 375°F (190°C), brush buns with egg wash, and bake 15–20 minutes until golden.