Warm the milk to about 30°C (86°F) and stir in yeast and sugar.
Mix flour, baking powder, and salt in a bowl. Add yeast mixture and stir until a rough dough forms (~4 mins).
Knead until smooth (~4 mins).
Place in an oiled bowl, cover, and proof for 1 hour or until doubled.
Punch down, divide into 8 pieces (~70 g each), and shape into balls. Rest 10 mins.
Roll into ovals (10 cm x 8 cm), brush one side with oil, fold in half, and place on parchment.
Proof 20–30 mins until puffed.
Steam 8–10 mins.
In a skillet over medium heat, sauté mustard greens, rock sugar, salt, garlic, and chilies.
Cook until the sugar dissolves. Adjust seasoning.
In a food processor, pulse peanuts, sugar, and salt until crumbly (not powdery).
Open a steamed bao.
Add 1 tablespoon of Haus relish.
Add a slab of red-braised pork belly (~10 cm / 4 in).
Top with crushed peanuts and cilantro.
