Mix the dough. Combine flour, milk, sugar, 2 of the eggs, the yeast, vanilla extract, and salt in the bowl of a stand mixer fitted with the dough hook attachment. Mix on low until the ingredients are combined. 

Add the butter. With the machine running, begin adding the butter a piece at a time, letting the first piece mix in before adding the next. 

Knead. Once all the butter has been added, increase the speed to medium and knead the dough for 8 minutes. 

The first rise. Grease a large bowl, add the dough and turn in the bowl to cover in oil. Cover bowl with plastic wrap and let rise in a warm place until doubled in size, about 4-5 hours. 

Make the topping. Combine flour, butter, sugar, milk, vanilla, and baking powder in the bowl of a stand mixer fitted with the paddle attachment. Mix until combined. 

Add flavorings. If you want to add cocoa powder, mix 2 tablespoons of cocoa powder to 1/2 cup of the topping. Knead the cocoa powder in with your hands in a separate bowl until well combined. 

To use freeze-dried fruit: Grind 1/4 cup of freeze-dried fruit in a clean coffee grinder or food processor until it is in a fine powder. Measure 1/2 cup of the topping into a separate bowl and add fruit powder. Knead into the topping until it is well combined. You can make as many flavors as you'd like. I was able to make 3 fruit flavors, chocolate, and vanilla with this amount of topping. 

Divide the dough. Once the dough has doubled in size, place dough on the counter and divide into 12 equal-sized pieces. The easiest way to do this is to weigh the dough on a kitchen scale, divide that number by 12, and then weigh out the pieces accordingly. 

Form the rolls. Taking one piece of dough and pinch all the ends together at one end to create a firm, round ball with a nipple on one side. Flip the ball nipple-side down on the counter and gently roll the ball to flatten it.  Repeat with remaining dough pieces. 

Place on baking sheets. Line two baking sheets with parchment paper. Place the rolls (6 on each baking sheet) with plenty of space in between. Beat the remaining egg and brush each roll with egg wash. 

Press the topping. The easiest way to get an even topping layer is to use a tortilla press. If you don't have one you can roll the topping with a rolling pin into a 1/4-inch thick circle. If you do have a tortilla press, scoop 2 tablespoons of the topping and press into a ball. The topping should be dry but still hold together. If it is completely falling apart on you, add 1/2 teaspoon of milk and try again. Place the topping ball between two sheets of plastic on a tortilla press and press into a 1/4-inch thick circle. Remove plastic and place evenly on a roll. 

Decorate the rolls. Gently form the topping around the top and edge of the roll. You can buy a stencil to create the design on top or use a sharp pairing knife like I did to create the design. Go with the traditional shell design or anything else you want to try—have fun with it! Cut through the topping, but not the roll. Repeat with remaining topping and rolls. 

Second rise. Cover the rolls with kitchen towels and let rise in a warm place until almost doubled in size, about 1-2 hours. 

Heat oven. Heat oven to 350°F and arrange the racks in the upper and lower third of the oven. 

Bake. Once conchas are risen, remove kitchen towels and place in the oven on the arranged racks. Bake for 20-30 minutes, switching the pans halfway through. Conchas are ready when they are golden and firm to the touch and sound hollow when you tap on the bottom.