Combine flour, yeast, sugar, and salt in a bowl. In a jug, mix warm water, milk, and oil. Pour wet into dry, stirring until a dough begins to form.

Transfer dough to a floured surface; knead for about 5 minutes until smooth and elastic.

Place dough in a greased bowl, cover, and let rise for about 1 hour until doubled in size.

Prepare the custard filling according to instructions, let cool slightly.

Punch down the risen dough, knead briefly, then divide into 12 pieces and roll into circles.

Place custard on one half of each circle, fold over and seal the edges. Let rest for 15 minutes.

Heat a non-stick pan over low heat, place buns leaving space, cover and cook for 10 minutes. Flip and cook for another 5 minutes.

Remove from pan, cool on a wire rack, dust with powdered sugar if desired, and enjoy warm.