Preheat oven to 425°. Lightly spray 8 (3 ½-inch) round tartlet pans with cooking spray.
On a lightly floured surface, unroll piecrust dough sheets. Using a 4-inch round cutter, cut 4 rounds from each dough sheet. Transfer each round to a prepared tartlet pan, pressing into bottoms and up sides. Using the wide end of a chopstick, gently press dough into indentations in sides of pans. Trim and discard excess dough. Using a fork, prick bottom of dough in each tartlet pan. Place tartlet pans on a rimmed baking sheet. Freeze for 15 minutes.
Place a square of parchment paper or a mini cupcake liner in center of each prepared tartlet pan, letting ends extend over edges of pans, and place ceramic pie weights, dried beans, or uncooked rice atop each parchment piece.
Bake until tartlet shell edges are lightly golden brown, approximately 7 minutes. Carefully remove pie weights and parchment paper, but do not remove tartlet shells from pans.
Bake tartlet shells for 3 minutes more. Let cool completely before carefully removing cooled tartlet shells from pans.
In a medium heatproof bowl, combine egg yolks, sugar, cornstarch, and salt, whisking thoroughly.
In a small saucepan, heat milk over medium-high heat until very hot, with bubbles around edges of pan and milk is steaming (do not boil), stirring occasionally. Whisking constantly, slowly add hot milk to egg yolk mixture. Strain mixture through a fine-mesh sieve into a medium saucepan. Cook over medium heat, stirring constantly until mixture thickens and comes to a low boil, 8 to 9 minutes. Remove from heat and stir in butter and vanilla extract until incorporated. Transfer pastry cream to a heatproof bowl and cover surface of pastry cream with plastic wrap. Refrigerate until cold, approximately 4 hours or up to a day in advance.
In a medium bowl, combine fruit and Jasmine Green Tea Syrup, tossing gently to coat fruit with syrup. Let soak for 30 minutes.
Divide cold pastry cream among tartlet shells, leaving room for fruit. Drain fruit well before arranging a layer of fruit atop pastry cream. Serve immediately, or cover loosely and refrigerate for up to an hour before serving.
Garnish with mint leaves, if desired.
Recipe by TeaTime Magazine at https://teatimemagazine.com/berry-cream-tartlets/