Fruit Mixture: 1 1/4 cups cubed rhubarb 1 1/4 cups cubed strawberries 2 tablespoons white sugar Dough: 2 cups all-purpose flour 2 1/2 teaspoons baking powder 1/2 teaspoon baking soda 1/2 teaspoon fine salt 1/2 cup (1 stick) frozen unsalted butter 1/4 cup white sugar 2 tablespoons reserved fruit syrup 3/4 cup cold buttermilk Egg Wash (optional): 1 large egg (optional) 2 teaspoons water (optional) Lā¦