To make the bao, mix the flour, baking powder, yeast and sugar in a large bowl. In a separate bowl, mix together the vegetable oil, water and milk. Make a well in the centre of the dry ingredients and pour in the oil mixture. Stir with a wooden spoon and then use your hands to knead until the dough comes together. Empty out onto a work surface and knead for 5 minutes or until smooth, adding extra flour if the dough sticks to the palm of your hand. Return the dough to the mixing bowl, cover and rest in a warm place for 90 minutes or until doubled in size. Once risen, transfer the dough to a work surface and knead for another 5 minutes. Place a small amount of oil in a small bowl. Flatten the dough and use a rolling pin to roll out the dough a little. Dip you fingers into the oil and rub on both sides of the dough to stop it from sticking to your work surface. Then continue to roll out the dough until it is about 1cm (roughly ½”) thick. Give the top of the dough a final rub of oil. Then use an 8cm (around 3 ¼”) cookie cutter to cut out dough circles. Fold each circle over in half and transfer to a square of baking paper. Use the rolling pin to roll over the top to gently flatten each folded piece. Any extra dough can now be rolled out again and cut and folded in the same way. Cover the bao lightly with a tea towel and allow to rise for 30 minutes. Fill a wok one-third full with water and place over high heat. Place a bamboo steamer over the wok. When the water is boiling, steam the buns in batches in the steamer for 12 minutes or until fluffy and cooked through. Then turn off the heat (don’t lift the lid) and allow the buns to rest over the hot water for 5 minutes before transferring to a plate or tray. Note: Buns can be made up to a day in advance and steamed to re-heat before serving. They can also be frozen at this point and reheated from frozen in the steamer before serving. To make the fried chicken, season the chicken with the salt and pepper, then set aside. For the sticky sauce, place the ingredients in a small saucepan over high heat. Bring to a simmer and cook for about 5 minutes or until just thickened. Set aside until ready to serve. Dust each piece of chicken in the corn flour, tapping off any excess. Fill a wok or saucepan to about 1/3 capacity with the vegetable oil and place over high heat. The oil is hot enough when a wooden spoon dipped into the oil forms little bubbles. Cook the chicken (do this in batches if your wok is small) for about 5 minutes or until golden and cooked through. Drain on a wire baking rack. Brush the warm chicken with the sticky sauce (reserve about a quarter of the sauce for serving). Sprinkle the chicken with sesame seeds. To serve, open up each bao and spoon a little sauce into the centre. Stuff with cucumber slices and pieces of fried chicken. Serve immediately. *NOTES: Gochujang is a Korean fermented chilli paste available in the Asian section of supermarkets or from an Asian grocer.