Hong Kong egg tarts

Ingredients:

Butter dough

• 3/4 cup premium flour
• 11 tablespoons chilled unsalted butter, cut into 1cm cubes

Dough on water

• 1 cup of premium flour + extra for work
• 0.5 tsp. granulated sugar
• 1/4 teaspoon coarse salt
• 1 large egg, beaten
• 3.5 tbsp cold water
• Special equipment: 12 tartlet moulds, 7.5 cm in size.

Egg filling

• 5 tbsp. whole milk
• 1/4 cup granulated sugar
• 2 large eggs
• 2 tbsp. unsweetened condensed milk
• 1/4 tsp vanilla extract

Preparation:

1. Butter dough:
   
   Place the flour and butter in a food processor and pulse until a thick, smooth paste forms, about 2 minutes. Spoon the dough onto plastic wrap and form it into a 5-inch (12.5 cm) square. Refrigerate until ready to use.
2. Dough on water:
   
   Place the flour, sugar, salt, and 3 tablespoons of beaten egg in a food processor (reserve the remaining beaten egg for the egg filling). Pulse several times to combine. Pour in the cold water, pulse until a rough, non-stick ball forms, about 2 minutes. Wrap the dough in plastic wrap and freeze for 20 minutes.
3. Egg filling:
   
   While the dough is resting, place the milk and sugar in a small saucepan and heat over high heat until the sugar dissolves, about 1 minute. Let cool completely, about 5 minutes.
4. In a large bowl, whisk the eggs with the reserved beaten egg until no visible egg whites remain, about 1 minute. Stir in the unsweetened condensed milk, vanilla extract, and cooled milk mixture. Strain the filling twice through a fine-mesh sieve into a measuring cup with a spout. Skim off any foam from the surface of the egg filling. Wrap the measuring cup in plastic wrap and refrigerate until ready to use.
5. Prepare the dough:
   
   On a lightly floured surface, roll the dough out into a 25cm square. Place the butter dough in a diamond shape in the center of the square. Fold the inner dough over the outer dough, brushing off any excess flour. Roll the dough out into a 12x30cm rectangle. Fold both short sides to the center, then fold in half, like closing a book. Wrap in plastic wrap and freeze for 20 minutes.
6. Roll the dough out into a 12x30 cm rectangle with the smooth side facing down. Fold both short sides toward the center, then fold in half, like closing a book. Wrap in plastic wrap and place in the freezer for 20 minutes. Repeat the entire process one more time.
7. After the dough has rested in the freezer for the last 20 minutes, roll it out on a lightly floured surface into a 27.5 x 35 cm (11 x 14 in) rectangle, just under 0.5 cm (0.2 in) thick. Using a 8 cm (3 in) cookie cutter, cut out 12 circles. Stack the circles, interleaved with plastic wrap, and place in the freezer to firm up, about 10 minutes.
8. Place one circle of dough into each of the twelve tartlet pans, pressing it up the sides. Place the pans on the prepared baking sheet. Prick the bottom of each tartlet three times with the tines of a fork. Refrigerate until the dough hardens, about 30 minutes.
9. Position the rack on the lowest shelf of the oven and preheat the oven to 190°C.
10. Carefully divide the egg filling among 12 lined cups (about 1 1/2 tablespoons each, stopping within 1/4 inch of the top). Bake the tartlets until the edges are starting to darken, 20 to 22 minutes. Reduce the oven temperature to 350°F (175°C) and continue baking until the crust is deep golden brown and the filling is slightly puffed, 13 to 15 minutes. Cool in the oven with the door ajar until the egg filling has softened, about 5 minutes. Transfer the baking sheet to a wire rack and let cool just enough to handle the tartlets, about 15 minutes. Remove the tartlets from the pans and enjoy slightly warm or completely cooled.