Brush brioche cups or muffin tin with the melted butter.
Sift together the flour, sugar and salt. Stir in the yeast. Add the warm water, eggs and remaining butter to make a soft dough.
Knead until smooth and then cover and let rise until doubled - approximately 1 1/2 hours.
Punch down and then divide dough in half. Shape the first half into 12 balls. Place each ball into a brioche or muffin cup and press an indentation into the center. Place a heaping teaspoon of Mascarpone into each indentation. Top with a square of chocolate. Press firmly into the dough ball.
Shape the remaining dough into 12 balls with a pointy end (like a tear drop shape). Brush each drop with milk and press into the brioche - pointy end up - sealing well.
Cover with oiled plastic wrap and allow to rise in a warm place until doubled in size - 1 to 1 1/2 hours.
Preheat oven to 400°F Brush with milk and bake 12-15 minutes until firm and golden brown.