In a large bowl, mix the flour, sugar, yeast, and salt.
Add the softened butter, warm milk, and eggs. Mix until a dough forms.
Knead the dough for about 10 minutes until smooth and elastic.
Place the dough in a greased bowl, cover, and let it rise for about 1 hour or until doubled in size.
For the topping, mix the softened butter, sugar, flour, and vanilla extract until smooth.
Divide the dough into 12 equal pieces. Shape each piece into a ball and place on a baking sheet.
Flatten a small amount of topping and place it on top of each dough ball. Use a knife to create a shell pattern.
Let the conchas rise for another 30 minutes.
Preheat the oven to 350°F (175°C). Bake the conchas for 20 minutes or until lightly golden.