Combine the plain flour, caster sugar and sea salt in a large bowl.

Dissolve the yeast and a pinch of caster sugar in 1 tbsp warm water.

Add the yeast mixture to the flour along with the milk, sunflower oil, rice vinegar and remaining warm water.

Mix into a dough, adding a little extra water if needed.

Transfer to a lightly floured surface and knead for 10–15 minutes until smooth.

Place into a lightly oiled bowl, cover and leave to rise for 2 hours until doubled in size.

Tip the dough onto a clean surface and knock back gently.

Sprinkle over the baking powder and knead for 5 minutes until fully incorporated.

Roll the dough into a long sausage shape around 3 cm thick, then cut into 8 equal pieces.

Roll each piece into a ball and leave to rest for 2–3 minutes.

Roll each ball into an oval roughly 3–4 mm thick.

Lightly brush the surface with sunflower oil. Place a lightly oiled chopstick across the centre, fold the dough over, then carefully remove the chopstick.

Place each bun onto a square of baking parchment.

Cover with a clean tea towel and leave to prove for 1 hour 30 minutes until doubled in size.

Steam over a medium-high heat for 8 minutes until puffed and cooked through.

Fill and serve warm.