Ina bowl, mix flour, eggs, milk, sugar, fresh yeast and salt until combined.
From that moment, in a stand mixer, knead the dough for 10 - 12 minutes or until it does not stick to the walls any more and gets elastic and shinny.
Then, add the chill butter and knead 10 more minutes.
Cover the dough with plastic wrap and let it proof in the refrigerator overnight.
The following day, dust some flour over the dough and work it a bit to deflate. Divide it into 10 portions, 50 gr each.
Round each portion using your hands in a circular motion and plat they with a kneading roll in discs of 7 cm diameter. If we want to get perfect round discs we can place the buns into 8 cm diameter metal rings that we will grease with butter and sprinkle some cane or brown sugar.
Let the buns proof for 1.5 - 2 hours at room temperature.
Vanilla chantilly
200 g heavy cream (35% fat)
50 g white sugar
5 g vanilla
In a bowl, pour cold heavy cream, add vanilla and start whipping at low speed with a hand blender.
Add sugar little by little while whipping the heavy cream to very soft peaks.
Assembly
After the brioche buns have proofed, make a small cavity at the center of each bun using your fingers, leaving a border of 1 cm width.
Then, fill the cavity with some vanilla chantilly.
Right after, sprinkle some caster sugar on top of each bun.
Bake for 10 minutes at 180º C and let the buns cool down to roomtemperature
Once the buns have cooled, brush each one with neutral graze and add some more vanilla Chantilly on top.
Lastly, add a teaspoon of blackberry jam atop each bun and decorate with one fresh blueberry. This kind of bun is best consumed the very same day they are baked due to the fact that they tend to dry out really fast.