1largeegg (or use a leftover egg white)+ 1 tbsp water
Sugar syrup
50gsugar
60gboiling water
Instructions
Make the Brioche Dough
In a stand mixer bowl fitted with a dough hook, add the milk and stir in the yeast and one tsp of sugar. Leave it to sit for 5-10 minutes until foamy. Add to it the remaining sugar, eggs, flour, and salt. Turn the mixer on low and combine until it forms a thick but slightly sticky dough. Mix this dough for around 5 minutes to begin developing the gluten.
Knead on medium speed for 5 minutes until the dough starts pulling away from the sides.
Gradually add the softened butter, a few cubes at a time, until fully incorporated. Knead for another 10-15 minutes until smooth and strong. Because it's only a small amount of dough, you might need to scrape down the mixing bowl sometimes.
Shape into a ball, place in a lightly greased bowl, cover, and let rise in a warm place for about 1-2 hours or until doubled in size. Alternatively, refrigerate overnight for better flavor.
Make the Pastry Cream
Heat the milk and vanilla in a saucepan until steaming. Remove from heat.
In a separate bowl, whisk egg yolks, sugar, salt and cornstarch until pale.
Slowly pour the hot milk into the egg mixture while whisking constantly.
Return the mixture to the saucepan and cook over medium heat, whisking constantly, until thickened. Whisk right away or else the cornstarch will start cooking too quickly at the bottom. Once thick, keep it at a bubble while whisking for around 45-60 seconds.
Remove from heat, stir in the butter, and transfer to a bowl. Cover with plastic wrap touching the surface and refrigerate until completely cold.
Assemble the Brioche Suisse
If you skipped the overnight refrigeration step, to make the shaping easier, I suggest chilling the dough for at least an hour to let the butter stiffen so it's not as soft. Roll out the brioche dough into a 30x25 cm (12x10 inches) rectangle on a lightly floured surface.
Use a whisk or fork to whisk the cold pastry cream up to be able to spread it. Spread the cooled pastry cream evenly over half the length of the dough. Sprinkle the chocolate chips on top.
Fold the other half of the dough over the filling, pressing gently to seal.
Cut into 6 even strips, about 5 cm (1.5 inches) wide.
Place them on baking sheets lined with parchment paper, spacing them slightly apart. Cover and let rise for 45-60 minutes, or until puffy.
Bake
Preheat the oven to 180°C (350°F).
Brush the pastries with egg wash.
Bake for about 18-20 minutes or until golden brown.
While pastries are in the oven, mix together the hot water and sugar until dissolved. Once the pastries are out of the oven, brush them with this syrup while they're still hot.