Vera Chan-Waller’s grandmother, Alice Chan, opened San Francisco’s Yank Sing back in 1958, and the restaurant has since become an icon. Its famous egg tarts are still made using Alice’s recipe. “They’re the perfect ratio of egg custard to crust,” Vera says.
Make the puff pastry: Cut the butter into 3/4 cup flour in a medium bowl with a fork, then knead with your hands until the dough comes together. Transfer the “oil dough” to a piece of plastic wrap and pat into a 7 1/2-inch square; wrap in the plastic and refrigerate 20 minutes.
Meanwhile, mix the egg, water and remaining 3/4 cup flour in a separate bowl, then knead with your hands until the dough comes together, adding more flour as needed if the dough is too sticky. Transfer the “water dough” to a piece of plastic wrap; wrap in the plastic and refrigerate 20 minutes.
Unwrap the “water dough” and roll out into an 11-inch square on a lightly floured surface. Place the “oil dough” square on top and turn it so that it looks like a diamond. Fold the sides of the “water dough” over the “oil dough” to enclose completely.
Roll out the folded dough into an 11-inch square and mark it into thirds. Fold in the outer thirds over the center third, like a letter. Roll out the folded dough into a large square again. Repeat twice (folding like a letter, then rolling into a square), refrigerating the dough as needed if it becomes too soft.
Mark the square of dough into fourths. Fold the outer fourths into the center, then fold in half like a book and roll out again. Wrap the dough in plastic wrap and refrigerate at least 20 minutes.
Butter 12 small (2 1/2- to 2 3/4-inch-diameter) fluted tart pans. Unwrap the dough and roll it out on a lightly floured surface to a 1/4-inch thickness. Cut out circles with a round cutter (about 1/4 inch larger than your tart pans). Refrigerate 20 minutes, then press the dough into the tart pans. Refrigerate until ready to use.
Make the egg custard: Heat the sugar and water in a saucepan over medium heat until the sugar dissolves, 3 to 5 minutes. Let cool completely.
Whisk the eggs into the cooled sugar syrup, then stir in the evaporated milk, vanilla and salt. Strain through a fine-mesh sieve into a large measuring cup.
Preheat the oven to 350˚ F. Arrange the tart pans on a baking sheet. Divide the custard among the pans, filling each about three-quarters full. (Do not overfill or the tarts could overflow; you may not use all of the custard.)
Bake until the crusts are golden and the filling puffs slightly, about 45 minutes. Let cool 5 to 10 minutes in the pans, then carefully tap the bottoms to remove the tarts and transfer to a rack to cool completely.