Follow the directions to make our brioche loaf bread up until the step 4, where it says you have to let the dough resting for it to double its size. Once the dough has doubled its size, put it in the fridge in the same bowl covered for 1 hour.
While the dough rests, to make the pastry cream, open the vanilla bean lenghtwise with a sharp knife and carefuly scrap out the seeds.
Put this in a pot over medium heat and add the milk along with the sugar. Let it cool for 2 minutes, being careful not to let it boil, mixing occasionally with a whisk.
In a different small bowl, using a fork, mix the rest of the sugar, salt, egg yolks, corn starch and flour together. Add in a little of the milk mixture to this mixture for it to temper.
Pour the egg yolk mixture into the milk pot and cook over medium low heat for about 4 minutes, beating non stop with a whisk until a thick cream forms. It is important not to stop beating and doing it carefully for the cream to be smooth.
Take the cream off the heat, add in the butter and beat until fully integrated. Pour the cream in a clean bowl, and cover it with kitchen plastic wrap (the plastic must touch the surface of the cream for it not to form a crust on top) and refrigerate for 30 minutes.
Once the brioche dough has cooled, put it on the kitchen countertop with some flour and roll it out to form a rectangle of about 17.70 x 11.80 inches (45 x 30cm) and about 0.20 inches (5mm) thick.
Add the cream on top of half the rectangle, spreading it out using a rubber spatula. Also on the same half add the chocolate chips.
Fold the other half of dough on top of itself to cover the filling and seal it all using your hands or the rolling pin to make it all be even.
Cut rectangles of about 1.18-1.60 inches (3-4cm) wide and place them on a big baking sheet lined with parchment paper. Cover them with kitchen plastic wrap or a kitchen towel and let them rest at room temoerature for 2 hours until they double their size.
A little before the resting time has passed, preheat the oven to 375º F (180º C). To finish, put the water along with the sugar in a small pot over medium heat and wait for the mixture to boil and for the sugar to completely dissolve and a syrup forms.
Once the breads have doubled their size, brush a mixture of beaten egg and milk on top and bake them for 12 to 14 minutes until they are slightly brown.
Take them out of the oven and brush the syrup on top. Let them cool down for 10 minutes and they are ready to eat.