Pear Ginger Galette with Hazelnut Crust

Name: Pear Ginger Galette with Hazelnut Crust
Ingredients: For the hazelnut crust:; 1/2 cup ice water; 2 tablespoons apple cider vinegar; 1/2 cup whole hazelnuts, toasted, skins removed; 1 1/8 cups all-purpose flour; 1/2 teaspoon salt; 1 1/2 teaspoons sugar; 1/2 cup cold unsalted butter, cubed; For the filling and assembly:; 5 medium pears; 1/4 cup packed light brown sugar; 1 tablespoon all-purpose flour; 1 teaspoon lemon juice; 1/8 teaspoon cinnamon; 1/8 teaspoon ground ginger; one 1-inch pieces fresh ginger, minced or grated; 1 egg, beaten with a splash of water; Coarse sugar, for sprinkling