Conchas (Mexican Sweet Bread)

To prepare the dough:

1. In a small bowl, sprinkle the yeast over the lukewarm milk. Stir briefly to combine and allow to sit at room temperature until frothy, about 10 minutes.
2. In the bowl of stand mixer fitted with a dough hook or a large bowl, combine the flour, sugar, and salt.
3. Mix in the yeast with milk, followed by the eggs, butter, and vanilla to bring the dough together.
4. On a lightly floured surface, knead dough until smooth and elastic.
5. Lightly oil a large bowl. Add the dough, turning to coat, cover, and let rise at room temperature until doubled, 1-2 hours.

To prepare the sugar crust:

1. While dough is rising, combine the flour, butter, powdered sugar, and cinnamon in a medium bowl.
2. Continue to mix to create a smooth dough.
3. Divide the sugar crust topping in half. Wrap one half in plastic wrap or cover.
4. Mix the cocoa powder with the remaining half of the dough topping until smooth. Wrap in plastic wrap or cover until ready to assemble.

To assemble:

1. Line 2 baking sheets with parchment or lightly grease.
2. Punch down dough and place on lightly floured surface.
3. Divide the dough into 12 equal pieces.
4. Form each piece into a smooth round and place on prepared baking sheet about 3 inches (7.6 centimeters) apart.
5. Divide each sugar crust dough half into 6 equal pieces to create 12 pieces in all.
6. Brush the tops of the buns with additional melted butter.
7. Roll one sugar crust dough piece into a ball and place between two pieces of plastic wrap or wax paper. Press into a thin circle.
8. Carefully remove the circle from the plastic and place over the butter-brushed bun, pressing down gently to make sure it is attached to the bun.
9. Repeat with the remaining pieces.
10. Use a sharp knife to cut angled lines or criss-cross patterns into the circles to resemble seashell shapes. Take care not to cut into the bread.
11. Cover the baking sheets and allow to rest at room temperature until the bread is puffed, 1-2 hours.
12. Preheat oven to 350˚F (180˚C).
13. Bake in the preheated oven until golden on the bottom, rotating the baking sheets halfway through, about 20 minutes total.
14. These Conchas are best the day they are baked.