In a food processor, blend flour, powdered sugar, and salt. Add cold butter and pulse until mixture resembles breadcrumbs. Add egg yolk and cold water; pulse until dough comes together. Wrap in plastic and chill for 30 minutes.

1. Preheat oven to 350°F (175°C). Roll out dough and cut rounds to fit mini tart pans or muffin tins. Press into molds and prick bottoms with a fork. Bake 12–15 minutes until lightly golden. Cool completely.
2. In a saucepan, heat milk until just simmering. In a bowl, whisk egg yolks, sugar, and cornstarch until smooth. Gradually whisk hot milk into yolk mixture, then return to saucepan. Cook over medium heat, whisking constantly, until thickened and smooth. Remove from heat, stir in butter and vanilla. Cover with plastic wrap touching surface and chill.
3. Spoon or pipe chilled pastry cream into cooled tart shells. Arrange fresh fruit decoratively on top.
4. Warm apricot jam with water, then brush over fruit to glaze. Chill until ready to serve.