In medium sized bowl, combine all the sponge ingredients, using spatula, cover tightly with transparent foil and leave to rise for 60 minutes.

Melt the butter in a small pot or microwave.

Add flour, milk, vanilla extract, salt, egg and butter to the sponge and combine roughly using spatula and continue combining using your hand.

Once you get sticky dough, add chocolate chips and combine.

Prepare egg wash.

Take the dough out of a bowl and divide to 12 equal parts.

Cover two sheet pan dishes with baking paper.

Preheat the oven to 180 C / 356 F.

Wet your hands and form balls: start by pulling the edges towards the center, turn the seam side down and circle using hands.

Turn each ball in your hands until the surface is smooth.

Place six balls in one sheet pan, leaving enough space to rise while baking.

Brush the balls with egg wash and leave to rest for 15 minutes.

Brush the balls with egg wash again and bake for 19 minutes.

The buns are golden on the top once done.

Repeat with the second baking dish.

Serve while still warm. You may spread them with simple layer of butter or cream cheese and add some fruits and syrup.