In a mixing bowl, combine all-purpose flour, cold unsalted butter, and granulated sugar until it resembles coarse crumbs. Gradually add cold water until the dough forms, then wrap in plastic wrap and refrigerate for 30 minutes.

Preheat your oven to 350°F (175°C). Roll out the chilled dough until about 1/8-inch thick. Transfer to a tart pan, pressing gently and trimming excess dough.

Blind bake for 15-20 minutes until lightly golden. Let cool completely on a wire rack.

Combine ripe mangoes, granulated sugar, eggs, lemon juice, and lemon zest in a saucepan over medium heat. Stir until thickened, about 10-15 minutes.

Remove from heat and whisk in chopped unsalted butter until smooth. Pour the curd into the cooled tart crust, smoothing the top.

Cover with plastic wrap and refrigerate for at least 2 hours. Garnish with fresh mint leaves and optional mango slices before serving.