Begin preparing galette dough: Roughly measure about ½ cup of ice water and set aside. In a large bowl whisk flour, half the granulated sugar, lemon zest and salt to combine. Using a box or handheld grater, grate frozen butter directly into bowl. Using clean, cold hands work the butter into flour mixture until only pea-sized and smaller pieces remain. Sprinkle egg yolk and 2 tablespoons of ice water over mixture and gently mix with hands, adding more ice water as needed until dough just comes together. Turn out onto a large piece of plastic, wrap tightly and work into the shape of a disc. Chill at least 30 minutes.
2 ½ cups all purpose flour, ¼ cup granulated sugar, 1 cup unsalted butter, 1 teaspoon salt, 1 teaspoon lemon zest, 1 large egg yolk, ¼ cup ice water
Meanwhile, prepare filling. Wash, dry and remove greens from fresh strawberries and thinly slice if berries are larger than ½". In a small bowl whisk lemon curd with lemon juice, remaining granulated sugar and cornstarch.
Roll chilled galette dough into a large ¼" thick round. Transfer to a parchment paper lined baking sheet then return to refrigerator to chill.
Preheat oven to 350 degrees Fahrenheit.
Either mound strawberry filling up into the center of the dough, or form concentric circles of layered berries. Pour remaining filling liquid over berries.
Fold pastry over creating a rough crust.
Whisk egg white until frothy and brush over crust. Sprinkle crust and filling with sugar.
1 large egg white, 2 tablespoons sugar
Bake until center is bubbly and crust is nicely browned, 55-65 minutes.