Directions

1. In a medium bowl, whisk together the egg, sugar, and cornstarch.
2. In a medium saucepan, bring the milk and lemon zest to a simmer over medium heat. Slowly whisk the hot milk into the egg, and then pour the egg-milk mixture back into the saucepan.
3. Return to low heat and whisk constantly for 1 minute as the mixture thickens to a custardy consistency, making sure to scrape the sides and bottom of the pan regularly so the texture is even. Dip a wooden spoon in and run your finger along the back of it: if the trace remains clear, the pastry cream is done.
4. Pour into a clean bowl and whisk in the lemon juice. Cover, pressing a piece of plastic wrap onto the surface of the custard, and refrigerate for a few hours until chilled. The pastry cream may be prepared up to a day in advance; whisk again before using.
5. Spoon the pastry cream onto the crust(s) and spread into an even layer. Arrange the strawberries over the cream in a circular pattern, starting from the center.
6. If desired, prepare a jam glaze to give the tartlets more shine: In a small saucepan, heat the jam with 1 tablespoon water until syrupy, without allowing it to boil. If the jam contains bits of fruit, strain it. Glaze the strawberries lightly with the syrup using a pastry brush. Let set for 10 minutes before serving.
7. Breton Shortbread Tart Dough
8. In the bowl of a stand mixer fitted with the paddle attachment, combine the sugar and butter. (Alternatively, do this by hand in a bowl with a wooden spoon.) Split the vanilla bean lengthwise with a sharp knife, scrape the seeds from the inside of the bean with the dull side of the blade, and add them to the sugar and butter (save the bean). Beat the sugar and butter at low speed until pale and fluffy, about 3 minutes. Add the egg and beat for 2 minutes.
9. In another bowl, combine the flour, baking powder, and salt, stirring with a whisk to remove any lumps. Add to the mixer and mix at low speed for a few seconds, just until no trace of flour remains. The dough will be quite soft.
10. Transfer the dough to an ungreased 10- to 12-inch / 25 to 30 cm round cake or tart pan with a removable bottom. Alternatively, arrange eight 3-inch / 8 cm pastry rings on a baking sheet lined with parchment paper or a silicone baking mat and divide the dough evenly among them. Press the dough into an even layer with a flexible spatula or the tips of your moistened fingers. Cover loosely with plastic wrap and refrigerate for at least 2 hours, and preferably overnight.
11. Preheat the oven to 350°F. / 175°C.
12. Bake until golden brown, 35 minutes for a single tart, 25 minutes for tartlets. Transfer to a rack to cool for 20 minutes before loosening and cautiously removing the sides of the tart pan or pastry rings. Let cool completely before topping. The crust may be prepared a few hours ahead; once cool, cover loosely with a clean kitchen towel.