In a stand mixer, combine flour, sugar, salt, and fresh yeast. Add eggs and knead the mixture until smooth—approximately 10 minutes. Gradually incorporate softened butter, kneading for another 15-20 minutes until the dough is sticky and elastic.

Gently cover the kneaded dough with plastic wrap and let it rise in a warm spot for about 2 hours, or until it has doubled in size. The dough should feel light and airy.

In a saucepan, heat whole milk and butter along with the split vanilla pod until warm. In a separate bowl, whisk egg yolks with sugar, cornstarch, and a bit of flour. Slowly mix the warm milk into the egg mixture, then return everything to the saucepan. Cook over medium heat, stirring constantly, until thickened. Chill the custard completely.

Roll the dough out into a large rectangle on a floured surface. Spread the chilled custard evenly, then sprinkle mini chocolate chips over the top. Fold the dough over, creating layers, and cut it into 8 equal pieces. Allow the pieces to rise for another 2 hours.

Preheat your oven to 350°F (180°C). Brush the tops of the risen brioche pieces with an egg wash for a golden finish. Bake in the preheated oven for 10-12 minutes, or until the brioches are golden brown and puffed up.

Mix equal parts boiling water and sugar to create a syrup. Brush the warm brioches with this syrup for a lovely shine, then let them cool on a wire rack before serving.