In a large mixing bowl, combine the all-purpose flour, active dry yeast, granulated sugar, and salt. Warm the milk slightly, then add it along with softened unsalted butter and eggs to the dry ingredients. Mix with a wooden spoon or dough hook for about 5–7 minutes until the dough is smooth and elastic.

Cover the dough with a clean kitchen towel and let it rest in a warm place for 1-2 hours, or until it has doubled in size.

In a saucepan over medium heat, combine the whole milk and granulated sugar, stirring until dissolved. In a separate bowl, whisk together egg yolks, vanilla extract, and cornstarch. Once the milk mixture is hot, slowly pour it into the egg mixture while whisking continuously. Cook for 5–7 minutes, stirring until thickened, then let cool.

Once the brioche dough has rested, gently punch it down to release air. Roll out the dough into a rectangle, spread the cooled vanilla custard evenly over the dough, and sprinkle chocolate chips on top. Roll the dough tightly into a log and cut it into equal portions, shaping each into individual brioches.

Place the shaped brioches onto a lined baking sheet, cover lightly with plastic wrap, and let them proof in a warm area for about 30–45 minutes, or until they are nearly doubled in size.

Preheat your oven to 375°F (190°C). Bake the brioches for 15–20 minutes until golden brown. Allow them to cool slightly before serving.