01 - In a food processor, pulse together flour, powdered sugar, and salt. Add cold butter and pulse until mixture resembles coarse crumbs. Add egg yolk and 1 tablespoon ice water, then pulse until dough just comes together, adding additional water 1 teaspoon at a time if needed. Transfer dough to lightly floured surface, gather into a disk, wrap in plastic, and refrigerate for 30 minutes.
02 - Preheat oven to 350°F. Roll out chilled dough to 1/8-inch thickness. Cut into circles sized to fit 8 mini tartlet pans measuring 3 inches in diameter. Press dough into pans and trim excess. Prick bottoms with fork, line with parchment paper, and fill with baking weights or dried beans. Bake for 12 minutes, then remove weights and parchment. Continue baking 5-8 minutes until golden. Cool completely.
03 - In a heatproof bowl, whisk together lemon juice, zest, sugar, and eggs. Set bowl over simmering water in a double boiler setup, whisking constantly until mixture thickens, approximately 8-10 minutes. Remove from heat and whisk in butter pieces until smooth. Strain curd through fine-mesh sieve into clean bowl. Cover surface with plastic wrap and refrigerate until set, at least 1 hour.
04 - Spoon or pipe lemon curd into cooled tartlet shells. Top each tartlet with fresh berries. Dust lightly with powdered sugar and garnish with mint leaves if desired. Serve chilled.