Chocolate Brioche Buns

1. In a small bowl, dissolve the yeast in warm milk (about 115 F) and the 1/2 tsp of sugar. Let it rest for about 10 minutes until it doubles in volume and foams up.
2. In a large bowl, combine flour, 1/4 cup sugar, and salt.
3. Add the yeast mixture and the egg to the flour. Mix everything well.
4. Add the softened butter and knead the dough on a lightly floured surface for about 10 minutes until smooth and elastic.
5. Place the dough in a greased bowl, cover with a clean cloth, and let it rise in a warm place for about 1-2 hours until it doubles in size.
6. Knead the dough briefly on a floured surface again, then divide it into equal portions. Form balls, flatten each into a disc, fill with chopped chocolate, and roll them up. Place on a baking sheet lined with parchment paper.
7. Cover the buns again and let them rest for another 30-45 minutes until they have risen. Brush with the whisked egg yolk and 1 tbsp milk mixture.
8. Preheat the oven to 350 degrees F.
9. Bake the buns in the preheated oven for about 15-20 minutes until golden brown.
10. Remove from the oven and let them cool completely before enjoying.