Sift bread flour and cake flour together.

Combine sifted flours, sugar, 20g butter, egg/milk mixture, milk, and yeast in a plastic bag.

Knead the dough in the bag for about 10 minutes until well combined.

Spread the dough out to about 2 cm thick inside the bag.

Fold the bag, leaving a little extra plastic at the opening.

Let the dough rise at 40C for 40 minutes using your oven's bread-rising function.

Knead 70g room temperature butter and 5g cake flour together evenly inside a plastic bag.

Spread the butter mixture into a block 22 cm wide by 20 cm long.

Chill the butter block in the fridge.

Press down on the risen dough to release the gas.

Reseal the bag and let the dough sit in the fridge for 25 minutes.

Spread out the bread dough wider than the chilled butter block.

Place the butter block in the center of the dough.

Fold both sides of the dough to the center, covering the butter like an envelope.

Stick the dough together in the center.

Flip the dough sideways so the seam is down.

Spread the dough out vertically.

Fold the dough into thirds.

Fold it in half once again, folding it twice as shown.

Wrap the dough in plastic wrap and let it sit in the fridge for 20 minutes.

Use a rolling pin to stretch the dough out.

Cut notches into the dough, creating three strips.

Adjust the sizes of the strips so they are even for braiding.

Let the dough rise a second time at 40C for 25 minutes using the oven's bread-rising function.

Bake at 200C for 10 minutes covered with aluminum foil to prevent burning, or bake at 170C for 20 minutes.