Little bites of heaven, these take a while to make but well worth the effort. Transport yourself to Portugal in one bite!
To make the dough, place the flour, salt, and water in the bowl of a stand mixer fitted with a dough hook. Mix for about 30 seconds until soft dough forms that cleans the side of the bowl.
Brush excess flour off the top of the dough, trim any uneven edges with a pastry cutter, and using a small offset spatula dot and then spread the left two-thirds of the dough with a little less than one-third of the butter to within 1 inch of the edge.
Neatly fold over the unbuttered right third of the dough using the pastry scraper to loosen it if it sticks, brush off any excess flour, then fold over the left third. Starting from the top, pat down the packet with your hand to release air bubbles, then pinch the edges closed. Brush off any excess flour.
Bring the sugar, cinnamon, and water to a boil in a small saucepan and cook until an instant-read thermometer registers 220°F. Do not stir.
Remove the cinnamon stick then pour the sugar syrup in a thin stream into the hot milk-and-flour mixture, whisking briskly. Add the vanilla and stir for a minute until very warm but not hot. Whisk in the yolks, strain the mixture through a sieve into a bowl, cover with plastic wrap, and set aside.
Heat the oven to 550°F for at least one hour. Remove the pastry from the refrigerator and roll it gently back and forth on lightly floured work surface until it’s about an inch in diameter and 15 inches long. Cut it into 1.25-inch pieces. Place the dough pieces cut-side down into each of the the 12 cups of the 12-cup muffin pan. Let the dough pieces soften several minutes until they become soft and pliable.
Fill each cup 3/4 full with the slightly warm custard. Bake the tarts until the edges of the dough are brown, about 10-12 minutes. If the tarts are not browning as much as you would like place them under a broiler for just a brief minute.
You can sprinkle the tarts generously with powdered sugar, then cinnamon before serving but it is optional.
Be sure to take note of the chill time a minimum of 2 hours is required and better if you can leave it overnight.
Try to remove as much flour as possible when working with the dough. The tart will get a bit tough otherwise.
Make certain to preheat your oven for at least one hour before baking.