In a large mixing bowl, combine all-purpose flour, sugar, salt, and active dry yeast. Gradually pour in warm milk (about 110°F) while stirring until a soft dough starts to form. Once combined, transfer the dough to a floured surface and knead for about 5 minutes until it becomes smooth and elastic.

Place the kneaded dough into a lightly oiled bowl, covering it with a damp cloth or plastic wrap. Allow it to rise in a warm location for approximately 1 hour or until it doubles in size.

After the dough has risen, punch it down to release any air. Divide the dough into 8 equal portions and roll each portion into a ball. Flatten each ball into a circle about 3–4 inches in diameter.

In a skillet over medium heat, cook your chosen filling until browned and cooked through. Add soy sauce and sriracha, cooking for another minute to incorporate flavors. Stir in chopped cabbage and cook until tender.

Place a generous spoonful of the filling in the center of each dough circle. Carefully fold the edges up and pinch them together to seal the bun tightly.

Line a bamboo steamer with parchment paper and steam the buns over simmering water for 15 minutes until fluffy.

Once steamed, carefully remove the bao buns from the steamer and serve warm.