In a tiny pan, combine water and flour and whisk.

Place it over low heat on the stove and keep whisking with a spatula, until you get a thick gel-consistency mixture (if you have a thermometer, wait until it reaches 65°C – 150°F)

Pour it on a plate, cover with plastic wrap and let it cool.

In your stand mixer's bowl, add flour, sugar, salt and activate at low speed (using the flat beater). After a few seconds, add dry yeast and warm milk (ideally at 35-40° C / 95°-104°F).

Add half of the egg (slightly beaten), powdered milk, cooled-down water roux, and let everything incorporate.

Add the butter (softened), change attachment with dough hook and let knead for about 10/15 minutes (or until gluten network has developed – read the post to know how)

NOW add the chocolate chips and let incorporate just a few seconds (otherwise they'll melt).

Place the dough into a slightly greased bowl, then cover with plastic wrap, and let it rise for 1.5 hours in a warm place.

After the dough has doubled, gently press it to degas it.

Divide it into 10 equal pieces and roll them into balls (pay attention not to handle them for too long otherwise chocolate will melt).

Place them on 2 separate baking trays (so they have "room" to rise), cover with plastic wrap and let rise for about 1 hour.

Preheat the oven at 180°C (350°F).

Make egg wash by combining remaining egg and milk, when buns are doubled brush them.

Bake for about 14 minutes.

As soon as you take them out of the oven, brush with more milk so they become softer.

Let cool down onto a cooling rack.