Instructions:
- Proof the yeast: In a small bowl, combine the yeast, 1 tsp sugar, and warm water. Let stand until foamy (about 5-10 minutes).
- In a stand mixer bowl, combine 4 cups + 2 tbsp flour, remaining sugar, and salt. Add the activated yeast mixture, warm milk, eggs, and vanilla extract. Mix on low speed until just combined.
- Knead on medium-low speed for 5 minutes. Gradually add the softened butter, one cube at a time, ensuring each piece is fully incorporated before adding the next. Continue kneading until the dough is smooth, elastic, and pulls cleanly away from the sides (about 10–12 minutes total kneading time).
- First Proofing: Place dough in a lightly oiled bowl, cover loosely, and let rise in a warm spot until doubled in size (approximately 1 to 1.5 hours).
- Prepare the Topping: In two separate bowls, divide the topping ingredients (1 ½ cups flour, 1 cup powdered sugar, ½ cup cold butter). In the first bowl, cut in the butter until coarse, then mix in ½ tsp vanilla to form the White Topping paste. In the second bowl, cut in the butter, then mix in the cocoa powder to form the Chocolate Topping paste.
- Roll out the toppings: Roll each topping mixture separately between two sheets of parchment paper until about 1/8 inch (3mm) thick. Refrigerate until needed.
- Shape and Second Proof: Gently punch down the dough. Divide into 12 equal balls (about 80g each). Shape into tight balls and place on parchment-lined baking sheets, spaced apart. Cover and proof for 45–60 minutes until puffy. Preheat oven to 375°F (190°C) during the last 15 minutes.
- Top the Conchas: Cut 12 circles from both the white and chocolate topping sheets. Place one circle on top of each dough ball (layering can create a two-tone effect). Use a sharp knife to lightly score a crosshatch or striped pattern onto the topping, taking care not to cut deeply into the dough.
- Bake for 18–22 minutes, rotating halfway through, until the bread is golden and the topping is set. Cool completely on a wire rack.