Place slightly colder than room temperature butter onto a sheet of parchment paper then form into a 6 x 6 inch and ~1/2 inch thick butter square.

Fold the sides of the parchment paper over the sides or place another sheet of parchment paper on top, so the butter is fully covered.

Then place into the refrigerator until it is cold and firm. Work on the dough while it is chilling.

In a mixing bowl, add warm water, dry active yeast and sugar.

Stir and let sit for 2 minutes.

Add salt and stir again.

Add melted butter, milk, and stir.

Slowly add flour, one cup at a time until a wet but not too sticky dough forms.

Knead dough with an electric mixer dough hook for about 3 minutes or knead by hand for about 4 minutes or until dough feels elastic and smooth.

Place 1/8 of a cup of flour onto a clean surface and roll dough out to form a square roughly 12 x 12 inches.

Remove the butter square from the refrigerator and unwrap it and place butter square so it looks like a diamond in the middle of your dough square.

Fold in the corner to form a box with the butter enclosed in dough.

Roll dough out to a rectangle roughly 14 by 16, then fold into 3 layers, each side folded in towards the center.

Wrap tri folded dough in plastic wrap or parchment paper and refrigerate for 20 minutes.

Remove plastic wrap or parchment paper and roll out again into roughly a 14 X 16 inch rectangle. Fold into thirds again, wrap again and refrigerate for 20 minutes again.

Repeat the same step again 4 more times, each of these folds is referred to as a turn, so we want a total of 6 turns.

After the final turn and refrigeration time, remove the wrap from the dough and roll out into a 14 x 16 inch rectangle again.

Cut into 12 equal sized rectangles.

There are two ways to roll these, one chocolate line or two. For one line; cut chocolate into 12 lines and then place the chocolate at the end of each of the rectangles and roll up dough then place on a lined baking sheet.

If you want a traditional style pain au chocolate with two lines you can cut chocolate into 24 lines and then place on the end of each side of the rectangle then roll each side towards the center so there are two chocolate lines going through the pastry. Place smooth side of rolled pastry up on a lined baking sheet.

Mix together the egg and water and then brush the tops of the pastries with it.

Sprinkle the tops with sugar and a light dash of salt.

Cover loosely with plastic wrap and let rise for 45 minutes or 1 hour or until pastries are doubled in size.

Preheat oven to 425 F.

Bake for ~15 minutes or until the pastries are golden brown on the tops.

Remove from the oven and let pastries cool slightly then dust tops with powdered sugar.

Enjoy!