Cut butter and shortening into 1/2” (1 cm) squares and put them in a medium-sized bowl. Transfer into freezer until hard, 15 minutes or so.

Line a strainer mesh srainer over a large bowl. Sift the flour over the strainer. Add the baking powder and salt. Stir to mix well.

Once the butter and shortening are fully chilled, add them into the flour mixture. Cut with a pastry cutter or using your fingers, until the mixture is mealy with some pea-sized chunks of butter.

Pour in the cold buttermilk. Stir with a spatula until a craggy dough forms. Add most of the green onion, saving about 2 to 3 tablespoons of it for garnish.

Lightly knead the dough in the bowl with your hand until it forms a dough ball, about 1 minute.

Chill the dough in the freezer for about 10 minutes, or cover with plastic wrap and chill in the fridge until ready to use.

Preheat the oven to 450 degrees F (232 C).

Dust your working surface with a thin layer of flour. Transfer the chilled dough onto it. Press the dough into a flat square. Cut the dough in half and fold it over itself. Repeat one more time.

Roll the dough with a rolling pin into a 1” (2.5 cm) thick sheet. Use a biscuit cutter to cut the dough into circles or you can use a knife to cut the dough into 2” (5 cm) squares. If using a biscuit cutter, you will have leftover dough. Gently gather the leftover dough together and press it until it just becomes one piece of dough (The more you handle the dough, the less it will rise during baking). Cut it into more biscuits.

Brush the top of the biscuits with a thin layer of milk.

Bake for 13 to 16 minutes, until the top turns light golden and the bottom turns golden brown.

Add the char siu drippings into a small saucepan. Heat over medium heat until hot.

Add the flour. Stir immediately until it’s fully incorporated.

Gradually add the stock, a few tablespoons at a time, and whisk constantly. It should start to form a thick paste. Once the paste turns smooth, add more stock and keep whisking. Continue until all the stock is fully incorporated with the flour.

Keep stirring and cooking, until the sauce has thickened enough to coat your spatula.

Add the char siu and the soy sauce. Cook for another minute until the meat is heated through. Taste the gravy. Add a pinch of salt and stir to mix well, if needed.

Sprinkle the remaining green onion onto the gravy and serve it with the fresh biscuits.

You can make the dish in advance and heat it up later. Heat the biscuits in the oven at 350 F (176) until heated through. Heat up the gravy in the microwave or on the stove top.