1 ½ cups all-purpose flour, plus additional for rolling
¼ teaspoon kosher salt
⅔ cup cold water, divided
¾ cup salted butter, at room temperature, divided
1 ¼ cups granulated sugar
⅔ cup water
1 teaspoon vanilla bean paste or extract
¼ teaspoon kosher salt
1 ¼ cups half-and-half or whole milk
2 tablespoons all-purpose flour
6 large egg yolks
Directions
To prepare the pastry, in a medium bowl, stir (or use your fingertips) to combine the flour, salt, and ½ cup water until the dough looks shaggy.
Transfer the dough to a clean countertop and lightly knead it to combine, adding remaining water as needed just until the dough comes together. Wrap the dough with plastic wrap and let it rest at room temperature for about 15 minutes.
Flour your surface and roll the rested dough to a 16- to 18-inch square.
Spread to coat the dough evenly with ½ cup butter, leaving a small border along the edges.
Cut slits in the square in thirds on the top and bottom, leaving the center ⅓ uncut.
Starting on the right, fold the top and bottom portions of the dough over the center.
Flip the right side square of dough over the center square. Fold over the top and bottom sections.
Repeat one final time with the remaining left side of the square.
Wrap the dough gently with plastic wrap and chill for at least 1 hour or overnight.
In the meantime, to prepare the sugar syrup, stir to combine the sugar, water, vanilla, salt, and cinnamon stick and lemon peel if you're using, in a small pot.
Bring to a boil, and continue to boil over medium heat for 1 minute.
Remove the pot from the heat. Discard the cinnamon stick and lemon peel if needed.
In another small pot, whisk the milk and flour to combine, and cook, whisking, until the mixture is scalding. Slowly whisk in the sugar syrup to combine. Remove from the heat.
Whisk the egg yolks in a medium bowl until smooth.
Slowly whisk about half of the hot milk mixture into the egg yolks.
Return the mixture to the pot and cook over low heat, whisking constantly, until thickened enough to just coat the back of a spoon. Avoid overcooking, which could cause it to curdle.
Strain the custard into a bowl and place plastic wrap directly on the surface. Chill until ready to use (or for up to two days).
Once the dough has chilled, transfer it back to a floured surface and roll to a 16x20-inch rectangle.
Spread to coat the dough with the remaining ¼ cup butter, leaving a small border along the edges.
Trim the edges and roll tightly starting on one of the short ends to form a log.
Pinch the seams to seal the log.
Cut the log in half, then refrigerate until cold (about 30 minutes to 1 hour).
Trim the ends, then use a sharp knife to cut each log into 8 to 9 slices.
Preheat the oven to 550 F.
Stir and let the custard filling stand, covered, at room temperature.
Grab two standard muffin pans and a small cup of cold water.
Wet your fingers, then press one section of dough into each well of the muffin pan, working it up the sides until the dough is evenly thin and coats the muffin well about ¾ of the way up. Avoid sealing the top edges of the dough as you work.
Repeat with the remaining dough sections, discarding any excess dough, to form 16 tarts.
Use a small scoop to portion the custard into each well, filling them about ¾ of the way to the top of the dough.
Bake one pan at a time (chilling the remaining pan in the refrigerator until ready to bake) for 10-12 minutes, keeping an eye on them using an oven light if possible, until the edges are golden and crisp, the center jiggles slightly, and the top has browned in spots.
Let the pan rest on a wire rack for 5 minutes before using a small paring knife to unmold the tarts onto wire rack (they'll be intensely hot).
Repeat with the remaining pan.
Serve warm, dusting the tarts with powdered sugar and cinnamon, if desired.