In a large mixing bowl, combine all-purpose flour, instant dry yeast, granulated sugar, and salt.

In a separate container, mix warm water, milk, and oil until well combined.

Pour this liquid mixture into the dry ingredients and stir until a soft dough forms.

Transfer the dough onto a clean, lightly floured surface and knead for about 5 minutes until smooth and elastic.

Place the dough in a lightly greased bowl, cover with a kitchen towel, and let it rise for approximately 1 hour.

While the dough is rising, prepare your custard filling according to the custard powder instructions and add vanilla essence if desired.

After the dough has risen, punch it down gently and knead again for about 3 minutes.

Divide the dough into 12 equal pieces, roll each into a circle about 3-4 inches in diameter, and place a spoonful of custard in the center.

Fold the dough over the filling, pinch to seal securely, and let the shaped buns rest for 15 minutes.

Preheat a non-stick pan over low heat, place the buns, and cover with a lid to cook for about 10 minutes until golden brown.

Gently flip each bun, cover again, and cook for another 5 minutes until fully cooked and fluffy.