Conchas (shells) are a Mexican pastry that is famous for its shape of a shell. The pastry contains a sugar shell pattern on the top. This is one of the most famous Mexican pastries recognized in the United States. It is also referred to as "pan de huevo".
In a large bowl stir together yeast and the warm water. Let stand for 10 minutes. Stir in evaporated milk, the 1/3 cup sugar, the melted butter, egg, and salt. Stir in 2 cups of the flour. Gradually stir in another 2 cups flour and the ½ teaspoon cinnamon to make a dough.
Turn the dough onto a lightly floured surface. Knead for 3 to 5 minutes or until smooth and elastic. Shape into a ball. Transfer dough to a large greased bowl; turn to coat surface of the dough. Cover and let rise in a warm place until double in size (1 to 1 ¼ hour).
Meanwhile, for topping, in a medium bowl beat the softened butter with an electric mixer on medium speed for 30 seconds. Add the 2/3 cup sugar, beating until well mixed. Stir in the 1 cup flour, the teaspoons cinnamon, and the vanilla.
Punch down the dough. Cover and let stand for 10 minutes. Divide dough into 12 portions. Shape each portion into a smooth ball. Place balls about 3 inches apart on baking sheets lined with parchment paper. Press down on balls slightly. Divide topping into 12 balls; pat each ball flat. Place one round of topping on each dough ball.
Using a sharp paring knife or concha cutter, cut grooves on a scallop shell. Cover rolls and let rise in a warm place until nearly double in size (about 45 minutes).
Meanwhile, preheat oven to 375 degrees F. Bake rolls for 18 to 20 minutes or until light golden brown. Remove from baking sheets. Cool on wire racks. Serve warm or cool.
Notes
Accompany this Mexican sweet bread with a hot cup of coffee or champurrado and the first warm bite will melt in your mouth.