Add the flour, salt, sugar, instant yeast, softened butter, water, and milk into a mixing bowl of a stand mixer, and attach the hook. Mix the dough on slow speed for 5 minutes, then increase the speed and mix for 3-4 minutes or until the dough is homogenized and developed.

Place the croissant dough into a lightly floured bowl or container, then place it into the refrigerator for 45 minutes. Remove the dough and turn it onto a lightly floured work surface and roll it out a 14×10-inch rectangle, cover it, and place it into the freezer for 30 minutes. You can also place the dough in the refrigerator for 3-4 hours or leave it overnight. Using my freezer method helps to speed up the process, I personally use this method in my bakery.

In the meantime prepare the butter slab. Slice the butter into 3 portions lengthwise and weigh it to make sure it is 220 grams.

Place the butter between a thick plastic or parchment paper, tap it a little bit with the roll pin, then roll it out to a 7X10 inch rectangle. You can also soften the butter using the mixing machine with the paddle attachment by mixing it for a few minutes, then and then spread the butter to size on parchment paper.

Once the butter is shaped into a rectangle, cover it and place it into the refrigerator to chill and set.

On a floured working surface, roll out the dough into a 14×10-inch rectangle. Place the butter slab in the center of the dough, then bring both ends of the dough together by folding it over the butter. Make sure both ends are sealed together.

Turn the dough over, then roll it out to 10X20 inches in length, then fold it into thirds, similar to folding a letter. Cover with plastic and place into the freezer for 30 minutes.

Repeat this process two more times, you will end up with 27 layers. Place the dough into the refrigerator for a minimum of one hour.

Line two baking pans with parchment paper and set aside.

Remove the dough from the refrigerator and transfer it onto a lightly floured work surface.

Roll out the croissant dough to a 19X11 inch rectangle, then using a sharp knife or pizza roller trim 1/2 inch from the top, bottom, and sides of the dough, you will end up with a 18X10 inch dough sheet. Discard the dough scrap or refrigerate or freeze it to use in another batch.

Using a measuring tape or ruler, measure and cut each dough piece into 5X3 inch rectangles, you should end up with 12.

To shape the pain au chocolat, face the shorted part of the dough piece towards you and place 1 chocolate baton or cut chocolate pieces about 1/2 inch from the bottom edge of the dough, then turn over the bottom side of the dough over the chocolate covering it, add another piece of chocolate against the end of the turned dough. Roll the croissant dough over again until it reached the top edge.

Gently press downwards to seal the seam, then place the pain au chocolat with the seam side down onto the lined baking pan.

Repeat this process until all the rectangles are shaped into pain au chocolate with the chocolate

When placing them on the baking pan make sure to space them apart about 2 1/2 inches.

Cover the baking tray with plastic and allow the croissants to proof at room temperature for 1 1/2 to 2 hours or until they double in size. You can also use your oven as a proofer by adding hot water into a bowl and placing it in the bottom of the oven, this will keep the oven humid allowing you to proof the croissants uncovered. When it is time to preheat the oven, remove them and let them stand at room temperature for about 15 minutes while the oven is heating up.

About 15 minutes prior to the croissants being fully proofed, preheat the oven to 400°F (200°C).

Brush the tops of the croissants with egg wash and bake for 18-20 minutes or until they are golden brown in color.

Remove from the oven and allow the pain au chocolat to cool on the pan for 5 minutes, then transfer to the cooling rack.

Enjoy!