Preheat oven to 350°F (175°C).

In a food processor, pulse flour and sugar to combine.

Add cold butter and pulse until mixture resembles coarse crumbs.

Add egg yolk and cold water, pulse until dough begins to come together.

Turn dough onto a floured surface and form into a disk. Wrap in plastic and chill for 30 minutes.

Roll out dough to about 1/8 inch thickness and cut into rounds to fit tartlet pans.

Press dough into the pans and trim excess. Prick bottoms with a fork.

Bake shells for 15-20 minutes until golden. Let cool completely.

In a medium heatproof bowl, whisk together eggs, sugar, lemon juice, and lemon zest.

Place the bowl over simmering water (double boiler), ensuring the bottom does not touch the water.

Cook, whisking constantly, until the mixture thickens enough to coat the back of a spoon (about 8-10 minutes).

Remove from heat and whisk in butter pieces until smooth.

Strain the curd through a fine mesh sieve into a bowl. Cover and chill until set.

In a bowl, beat mascarpone, powdered sugar, and vanilla extract until smooth.

Spread a layer of lemon curd into each cooled tart shell.

Top with a generous layer of mascarpone filling.

Arrange sliced strawberries on top of the mascarpone layer.

Garnish with fresh mint leaves if desired.

Refrigerate tartlets for at least 1 hour before serving.