In a food processor, combine flour, powdered sugar, and kosher salt. Cut in cold, cubed unsalted butter until the mixture resembles pea-sized crumbs. Add beaten egg and vanilla extract, blending until a smooth dough forms. Wrap the dough in plastic wrap and chill in the refrigerator for 1 hour.

Preheat your oven to 350°F (175°C). Roll out the chilled dough to about ¼-inch thickness. Cut out circles and fit them into mini tart pans. Freeze the tart shells for 20 minutes before baking. Bake for 15 to 20 minutes, or until golden brown. Cool completely before filling.

In a medium saucepan, heat whole milk and vanilla extract until just simmering. In a separate bowl, whisk together sugar and cornstarch. Gradually add half of the hot milk to the starch mixture, whisking continuously. Temper the egg yolks with the mixture before returning everything to the saucepan. Cook over low heat until thickened and smooth, about 5-7 minutes. Cool in the fridge.

Using a piping bag, fill each cooled tart shell with pastry cream. Arrange fresh fruits on top.

Heat apricot jam and water until melted. Brush this mixture lightly over the fruit to add shine. Allow to set before serving.