In a large mixing bowl, combine 1 ¼ cups of all-purpose flour, ¼ cup of granulated sugar, and ½ cup of unsalted butter cut into cubes. Use a pastry cutter or your fingers to mix until the mixture resembles coarse crumbs. Add the yolk of one large egg and 2 to 4 tablespoons of ice water, mixing until the dough forms. Chill the dough for 30 minutes before rolling it out.

Preheat your oven to 375°F (190°C). Once chilled, roll out the dough on a floured surface until about 1/8-inch thick. Carefully fit the dough into tartlet tins, trimming any excess. Prick the bottoms with a fork to prevent bubbling. Line with parchment paper and fill with pie weights or beans. Bake for 15-20 minutes, or until golden brown. Remove from the oven and let the shells cool completely.

In a medium saucepan over medium heat, whisk together 3 large eggs, ½ cup of granulated sugar, ⅓ cup of fresh lemon juice, and the zest of one lemon. Stir continuously for about 5-7 minutes until the mixture thickens and coats the back of a spoon. Remove from heat, then stir in 4 tablespoons of unsalted butter until melted and fully incorporated. Allow to cool before using.

In a mixing bowl, beat 1 cup of mascarpone cheese with ½ cup of heavy cream, ¼ cup of powdered sugar, and 1 teaspoon of vanilla extract. Whisk until the mixture is light and airy, forming soft peaks; this should take about 3-5 minutes. Set aside, keeping it chilled until you're ready to assemble the tartlets.

Once the tartlet shells are completely cooled, fill each one generously with the mascarpone filling. Using a spoon, swirl in a layer of lemon curd atop the mascarpone. Finally, slice fresh strawberries and artfully arrange them on top of the curd.

Cover the assembled tartlets with plastic wrap and refrigerate them for at least 1 hour. This chilling time allows the flavors to meld and the fillings to firm up. Just before serving, dust with powdered sugar for an elegant finishing touch. Enjoy these beautiful Strawberry Mascarpone Tartlets with Lemon Curd as a delightful summer treat!