Steps
1. Prepare the walnut sweet shortcrust: Combine flour, powdered sugar, ground walnuts, and salt. Rub in cold butter until mixture resembles breadcrumbs. Add a splash of cold water and knead lightly to form dough. Wrap and chill for 30 minutes.
2. Preheat oven to 180°C (350°F). Roll out dough into a 12cm tart tin. Prick base and bake blind for 12-15 minutes until golden. Cool completely.
3. Make the pastry cream: Heat milk to just below boiling. Whisk egg yolk, sugar, and cornstarch until smooth. Gradually pour hot milk into egg mixture, stirring continuously. Return to heat and cook until thick. Remove from heat, add vanilla, and cool.
4. Prepare coffee chantilly: Whip heavy cream with coffee powder and powdered sugar until soft peaks form. Refrigerate.
5. For the pitaya glaze: Warm pitaya pulp with sugar syrup. Stir in melted gelatin until fully combined. Cool slightly.
6. Assemble the tart: Fill baked tart shell with pastry cream. Pipe or spread coffee chantilly cream over the custard.
7. Pour the pitaya glaze evenly on top to create a shiny layer.
8. Garnish with fresh mint leaves, crushed walnuts, and a light dusting of powdered sugar.
9. Chill tart for at least 1 hour before serving to set glaze and flavors.