280g/10oz strong white flour, plus extra for dusting
pinch caster sugar
2 tbsp vegetable oil
1 tsp custard powder
1 tbsp black sesame seeds
For the dipping sauce
50ml/2fl oz Chinese black vinegar
1 tbsp grated fresh root ginger
1 tbsp chilli oil
2 tsp caster sugar
50ml/2fl oz soy sauce
To make the filling, cover the dried mushrooms in hot water and leave to soak. Once they are plump, drain and finely chop.
Heat the oil in a frying pan and sauté the onion, garlic, ginger and cumin for 5 minutes, or until the onions are softened. Add the aubergines and mushrooms and stir in the hoisin sauce. Pour in the stock and stir in the cornflour. Season with soy sauce and pepper, to taste, and cook for 5–10 minutes, or until the aubergines are softened. Set aside and leave to cool before using to fill the buns.
For the baked buns,Mix the yeast with 100–120ml/3½–4fl oz of water in a small bowl. Place the flour, sugar and salt in a mixing bowl, create a well in the middle and pour the yeast into the well. Pour in the oil and knead the dough for 10–15 minutes, or until a smooth dough is formed. Place the dough back in the bowl, cover with a tea towel and leave to prove in a warm place for 1 hour. Knock back the dough on a floured work surface and roll into small balls.
Preheat the oven to 180C/200C Fan/Gas 4. Roll the balls out into rounds that are about 5cm/2in in diameter. Pull the outside edges gently so they are a little thinner than the middle of the rounds.
Fill the centres of the rounds with some of the aubergine mixture, fold over the dough and crimp the buns closed with a fork. Place on a baking sheet lined with baking paper, crimped-side down. Mix the custard powder with 1 tablespoon of water in a small bowl. Brush the buns with the custard powder glaze, sprinkle over the black sesame seeds and bake for 15–20 minutes.
Mix all of the dipping sauce ingredients together in a small bowl. Serve the baked buns with the dipping sauce alongside.