For the brioche:

1. In the bowl of a kitchen aid with a paddle attachment, add the flour, sugar, salt and crumbled yeast, making sure salt and sugar don’t interact with the yeast. Mix quickly.
2. Add the eggs and knead for about 2-3 minutes at medium speed, until the dough become strong and thick.
3. Incorporate the diced softened butter in several additions while the kitchen aid is running at medium speed. Knead until butter is completely incorporated and the dough becomes dense, smooth and slightly sticky, about 20 minutes.
4. Place the dough in a clean medium size bowl, cover with cling film and let rise in a warm room for about 2 hours or until the dough has doubled in size.
5. Flatten the dough in a thick rectangle, wrap with cling film and place in the refrigerator for about 40 minutes (until 2 hours if you have time), and in the freezer for 20 minutes.

For the vanilla custard (crème pâtissière):

1. Heat milk and butter on medium heat. Add the vanilla pod and grated seeds.
2. In a separate bowl, whisk the yolks with sugar. Pour in the flour and cornstarch, and whisk until well combined.
3. When the milk is bubbling, remove the vanilla pod and pour the milk over the egg mixture in a few additions until well combined.
4. Pour the mixture back in the pan on low-medium heat, and keep whisking until it thickens.
5. Transfer into a clean bowl, cover with cling film, making contact with the vanilla custard. Place in the refrigerator until ready to use.

For the filling and brushing:

1. Remove the dough from the fridge and roll it out on a clean surface covered with parchment paper in a large rectangle of 8×12 inches (40×30 cm). Cover half of the dough with the custard vanilla, lengthwise.
2. Sprinkle the chocolate chips over, and gently use the rolling pin to make pressure so the chocolate chips make contact in the custard.
3. Fold in the empty side of the dough over the garnished one, and flatten the top part with your hands to empty the possible air bubbles. Gently flatten with a rolling pin to make sure the surface is smooth.
4. Using a sharp knife, cut the dough in 8 equal rectangles, about 1 to 1.5 inch (3 to 4 cm) wide. Place each of them on a prepared baking sheet lined with parchment paper, leaving enough space between each of them. Cover with cling film and let rise for 2 hours.

For the syrup and brushing:

1. In a small saucepan, bring to boil sugar and water, until sugar is completely dissolved. Let cool.
2. When the brioches are ready, brush them with the beaten egg and yolk, then bake in a pre-heated oven at 350°F (180°C) for 10-12 minutes, or until golden-golden brown, depending on your preference.
3. Remove from the oven and brush with the syrup right away. Let cool completely before serving.