Bake Tart Shell(s)

1. With a stand or hand mixer, beat butter, sugar, and salt on medium-high speed until smooth and lightened in color.
2. Add the egg and beat it in well, scraping down the bowl and paddle as you go.
3. At low speed, slowly add flour until the dough comes together in a cohesive mass. Form into a flat disc, wrap in plastic, and chill for at least two hours. This can be done a few days ahead and chilled, or frozen.
4. On a lightly floured surface or between pieces of parchment paper, roll dough to a quarter-inch thickness, and at least an inch larger than your tart pan.  For mini tarts, use a knife to cut out circles a little larger than your pans. 
5. Gently press the rolled dough into the bottom and up the sides of a 9" or 11' tart pan with a removable bottom (or mini tart pans). Roll the pin along the top of pan(s) then remove any excess dough. Poke holes, or "dock" the bottom of the dough with a fork.
6. Freeze the shells for twenty minutes. Preheat oven to 350° F. Line the shells with foil or crumpled parchment paper and fill with pie weights, dried beans, spare change, or rice.
7. Bake mini shells for 10 to 20 minutes, remove the weights, and bake until edges begin to brown and the bottom appears cooked through. A large tart will need more time, around 20 minutes with the weights, and then 20 more minutes after removing them.
8. Cool the tart shells completely before removing it from the pan(s). Use a small, sharp knife to chip away any crust that is preventing easy removal. 

Prepare Pastry Cream

1. Combine half of the sugar, salt, and half of the milk in a medium pot. Bring just to a boil over high heat. 
2. While the mixture is coming to a boil, combine the cornstarch and remaining sugar in a medium heatproof bowl. Whisk in the remaining milk to make a slurry (thick starch-liquid mixture). Then gently stir the eggs into the slurry.
3. Once the milk reaches a boil, slowly pour the hot mixture into the egg mixture, whisking vigorously. This tempers the heat into eggs so they don’t curdle or scramble.
4. Pour the tempered egg mixture back into the pot, and turn the heat down to medium. Whisk constantly until pastry cream comes to a slow boil, with just a few large bubbles breaking the surface.
5. Pour the cream into a bowl, whisk in the vanilla extract or vanilla seeds and the butter until it's melted, and press plastic wrap over the surface. If your cooked cream has lumps, you can strain it through a fine-mesh sieve. Poke a few holes in the plastic wrap to allow steam to escape the cream, and cool in the refrigerator.
6. Fill the baked tart shells with the chilled pastry cream and top with your fruit, or follow the directions below to make diplomat cream (pastry cream lightened with whipped cream).

Diplomat Cream

1. Only prepare diplomat cream right before building your tarts. Whip the heavy cream with sugar on medium speed to soft peaks, and fold gently into the pastry cream until combined. 
2. Transfer the cream to a pastry bag (no tip) or large plastic baggie, and snip one corner to make a half-inch hole. Pipe or spoon the pastry cream into the baked tart shells so it comes almost all the way up the sides. 
3. Layer fresh fruit on top and brush with the warmed apricot jam. Store chilled, serve room temperature.