In a large mixing bowl, combine all-purpose flour, sugar, and salt. Crumble in the fresh yeast, followed by beaten eggs and softened unsalted butter. Mix well until a shaggy dough forms, then knead on a floured surface for about 20 minutes until smooth and elastic.

Transfer the kneaded dough to a greased bowl, cover with a damp cloth or plastic wrap and allow to rise for approximately 2 hours until doubled in size.

In a saucepan, heat whole milk and a small piece of butter along with the scraped vanilla seeds. In a separate bowl, whisk together egg yolks, sugar, and cornstarch, then gradually add the warm milk mixture.

Cook the custard over medium heat for about 5 minutes until thickened, then let cool completely.

Once the brioche dough has risen, punch it down, roll it out, spread the vanilla custard, sprinkle mini chocolate chips, fold like a letter, then cut into 2-inch pieces.

Cover the shaped brioches with a cloth and let them rise again in a warm environment for another 2 hours.

Preheat the oven to 350°F (180°C). Whisk an egg and egg yolk for the egg wash, then brush over the tops of the risen brioches.

Bake in the preheated oven for 10-12 minutes until golden brown.

Prepare a simple sugar syrup by boiling equal parts water and sugar, then brush it over the baked brioches.

Allow the brioches to cool for a few minutes before transferring them to a wire rack. Enjoy warm.