Blueberry Rhubarb Galette

Name: Blueberry Rhubarb Galette
Cuisine: European, Mediterranean, French
Ingredients: 1-1/2 cups all-purpose flour; 2 tablespoons sugar; 1/2 teaspoon salt; 6 tablespoons cold butter, cut into cubes; 1/3 cup ice water (you may not need all of this); 2 cups blueberries; 2 cups rhubarb, sliced; 3/4 cup sugar; 2 tablespoons flour; 2 tablespoons quick cooking tapioca; 1/4 teaspoon salt; 1/8 teaspoon freshly grated nutmeg; 1 tablespoon freshly squeezed lemon juice; 1 egg, lightly beaten; 1 tablespoon milk; 2 tablespoons sugar, for sprinkling (turbinado sugar is nice here, but granulated works, too)