Heat oil in a skillet over medium heat.

Saute scallions, garlic, and ginger until fragrant.

Stir in hoisin sauce and oyster sauce.

Add char siu pork and stir to combine.

Reduce heat to low.

Combine cornstarch with 2 tablespoons of water to make a slurry.

Pour cornstarch slurry over pork mixture and stir until the sauce thickens.

Set aside the pork filling to cool.

On a floured surface, partially separate the breadsticks dough, leaving two thick layers.

Roll each layer of dough into a ball.

Working with one ball at a time, roll it out to create a 3-inch circle.

Place about 1 tablespoon of the pork filling in the center of each dough round.

Gather the dough up around the filling and twist to secure tightly, forming a bun.

Repeat with the remaining dough and filling.

Cover the assembled buns with a kitchen towel.

Arrange Napa cabbage leaves on the bottom of two large bamboo steamers.

Place 6 pork buns on each steamer.

Steam the buns for 20 minutes, or until cooked through.

Serve the steamed pork bao buns warm.