In a small pot, combine 2 cups of fresh blueberries with sugar and a splash of water. Mix together cornstarch and remaining water, and add it to the pot. Cook over medium heat, stirring frequently, until thickened and blueberries burst, about 5 minutes. Set aside to cool.

Grate the zest of two lemons and juice them. In a medium pot over low to medium heat, whisk together egg yolks, sugar, and lemon juice. Cook, stirring continuously until thickened about 10 minutes; do not let it boil. Remove from heat and whisk in cold butter and lemon zest until smooth. Transfer to a bowl to cool in the refrigerator.

Prepare the tart shell by rolling out the chilled dough and placing it into a tart pan, pressing gently into the edges. Prick the bottom with a fork and bake at 350°F (175°C) for 20-25 minutes or until golden brown. Allow to cool completely.

Pour the cooled lemon curd into the cooled tart shell, spreading evenly with a spatula.

Spoon the cooled blueberry compote over the lemon curd, letting some blueberries tumble over the edges.

Cover the tart with plastic wrap and refrigerate for at least 2 hours or overnight. This allows the flavors to meld and lets it set.

When ready to serve, slice the tart into wedges and garnish with powdered sugar or fresh mint.