Strawberry-rhubarb Pie, Improved

Ingredients

• 1 recipe all butter, really flaky pie dough or double-crust pie dough of your choice
• 3 1/2 cups (about 1 1/2 pounds, untrimmed) rhubarb, in 1/2-inch thick slices
• 3 1/2 cups (about 1 pound) strawberries, hulled and sliced if big, halved if tiny
• 1/2 cup granulated sugar
• 1/4 cup light brown sugar
• 1 tablespoon lemon juice
• 1/4 teaspoon salt
• 1/4 cup quick-cooking tapioca
• 2 tablespoons unsalted butter, cut into small pieces
• 1 large egg yolk beaten to blend with 1 teaspoon water (for glaze)