1 Roll out the shortcrust pastry on a floured surface to about 3mm thickness. Cut the pastry into circles that will fit your tart tins
2 Gently press the pastry circles into the tart tins, making sure to trim any excess. Prick the bottom of the pastry with a fork and bake in the preheated oven (200C/fan180c/gas 6) for about 15 minutes or until the pastry is golden brown, then allow to cool.
3 In a mixing bowl, combine the Galbani mascarpone, caster sugar, lime zest, and finely chopped Kaffir Lime leaves. In a separate bowl, mix the lime juice and cornflour until smooth.
4 Add the lime juice mixture to the mascarpone mixture and blend until well combined.
5 Beat in the eggs one at a time until the filling is smooth and creamy.
6 Spoon the mascarpone mixture evenly into the cooled pastry then bake at 160°C for 15-20 minutes, until the core temperature reaches 70°C
7 In a saucepan, combine the sugar and water. Heat over medium heat until the sugar dissolves and the mixture reaches 121°C on a candy thermometer.
8 While the sugar syrup is cooking, start whipping the egg whites in a clean, dry bowl until they form stiff peaks.
9 Once the sugar syrup reaches 121°C, slowly pour it in a thin stream into the whipped egg whites while continuously beating at high speed. Continue to beat the meringue until it cools to room temperature, and it becomes thick and glossy.
10 Spoon or pipe the meringue topping onto the filled tarts, covering the mascarpone filling completely. Use a kitchen torch to carefully brown the meringue on top. Alternatively, you can place the tarts under a preheated grill for a few seconds.
11 Once the meringue is browned to your liking, refrigerate the tarts for at least 2 hours or until they are set. Finish with grated lime zest.