Portuguese Egg Tart (Pastel de Nata)

Make the pastel de nata dough

1. In a stand mixer fitted with a dough hook, mix the all-purpose flour, sea salt, and cold water until a soft, pillowy dough forms that pulls away from the side of the bowl, about 30 seconds.
   
2. Generously flour a work surface and pat the dough into a 6-inch square using a pastry scraper. Flour the dough, cover with plastic wrap, and let it rest at room temperature for 15 minutes.
   
3. Roll the dough into an 18-inch square. As you work, use the scraper to lift the dough to make sure the underside isn't sticking to your work surface. Add extra flour as needed.
   
4. Brush the excess flour off the top of the dough, trim any uneven edges, and, using a small offset spatula, dot and then spread the left 2/3 portion of the dough with a little less than 1/3 of the butter being careful to leave a 1 inch plain border around the edge of the dough.
5. Neatly fold the unbuttered right 1/3 of the dough over the rest of the dough. Brush off any excess flour, then fold over the left 1/3 of the dough. Starting from the top, pat down the dough with your hand to release any air bubbles, and then pinch the edges of the dough to seal. Brush off any excess flour.
6. Turn the dough 90° to the left so the fold is facing you. Lift the dough and flour the work surface. Once again roll it out to an 18-inch square, then dot the left 2/3 of the dough with 1/3 of the butter and smear it over the dough. Fold the dough as directed previously.
7. For the last rolling, turn the dough 90° to the left and roll out the dough to an 18-by-21-inch rectangle, with the shorter side facing you. Spread the remaining butter over the entire surface of the dough.
8. Using the spatula to help, lift the edge of dough closest to you and roll the dough away from you into a tight log, brushing the excess flour from the underside as you go. Wrap in plastic wrap and chill for 2 hours or preferably overnight. (The pastry can be frozen for up to 3 months.)
   

Make the custard

1. In a medium bowl, whisk the all-purpose flour and the milk until smooth.
   
2. Bring the granulated sugar, cinnamon stick, and water to a boil in a small saucepan and cook until an instant-read thermometer registers 220°F. Do not stir.
3. Meanwhile, in another small saucepan, scald the remaining milk. Whisk the hot milk into the flour mixture.
4. Remove the cinnamon stick and then pour the sugar syrup in a thin stream into the hot milk-and-flour mixture, whisking briskly. Add the vanilla extract and stir for a minute until very warm but not hot.
   
5. Whisk in the egg yolks, strain the mixture into a bowl, cover with plastic wrap, and set aside. The custard will be thin; that is as it should be. (You can refrigerate the custard for up to 3 days.)
   

Assemble and bake the pastries

1. Place an oven rack in the top third position and crank the oven to 550°F for at least 30 minutes. The oven needs this time to maintain this blazing hot temperature.
2. Remove a pastry log from the refrigerator and roll it back and forth on a lightly floured surface until it's about an inch in diameter. Cut it into scant 3/4-inch pieces. Place 1 piece pastry dough, cut side down, in each well of a nonstick mini-muffin pan (2-by-5/8-inch size).
   

3. Have a small cup of water nearby. Dip your thumbs in the water, then straight down into the middle of the dough spiral. Flatten it against the bottom of the cup to a thickness of about 1/16 inch, then smooth the dough up the sides. The pastry bottoms should be thinner than the tops.

   
4. Fill each cup 3/4 full with the cool custard. Bake the pastries until the edges of the dough are frilled and brown, about 8 to 9 minutes for the mini-muffin tins, 15 to 17 minutes for the classic tins.
   
5. Remove from the oven and allow the egg tarts to cool a few minutes in the pan, then transfer to a rack and cool until just warm. Sprinkle the pastries generously with powdered sugar, then ground cinnamon and serve. Repeat with the remaining pastry and custard. These are best consumed the day they're made.