2 Tablespoons unsalted butter, cut into small pieces
1 large egg, lightly beaten with 1 Tablespoon (15ml) milk
optional: coarse sugar for garnish
Make the filling: Stir the rhubarb, strawberries, brown sugar, granulated sugar, cornstarch, salt, orange juice, and vanilla extract together in a large bowl. Set filling aside as the oven preheats.
Preheat oven to 400°F (204°C).
Roll out the chilled pie dough: On a floured work surface, roll out one of the discs of chilled dough (keep the other one in the refrigerator). Turn the dough about a quarter turn after every few rolls until you have a circle 12 inches in diameter. Carefully place the dough into a 9×2 inch pie dish. Tuck it in with your fingers, making sure it is smooth. Spoon the filling into the crust, leaving all of the excess liquid in the bowl (you don’t want that in the filling– discard it). Dot the pieces of butter on top of the filling.
Arrange the lattice: Remove the other disc of chilled pie dough from the refrigerator. Roll the dough into a circle that is 12 inches diameter. Using a pastry wheel, sharp knife, or pizza cutter, cut strips 1/2 – 1 inch wide. Carefully thread the strips over and under one another, pulling back strips as necessary to weave. Press the edges of the strips into the bottom pie crust edges to seal. Use a small knife to trim off excess dough. Crimp the edges with a fork, if desired. (Alternatively, you can simply cover the filling with the 12-inch pie dough circle. Cut slits in the top to form steam vents. Trim and crimp the edges. Crumble or streusel topping is also an option
Lightly brush the top of the pie crust with the egg/milk mixture. Sprinkle the top with a little coarse sugar, if desired.
Place the pie onto a large baking sheet and bake for 20 minutes. Keeping the pie in the oven, turn the temperature down to 350°F (177°C) and bake for an additional 25-30 minutes. After the first 20 minutes of bake time, I place a pie crust shield on top of the pie to prevent the edges from browning too quickly.
Allow the pie to cool for 3 full hours at room temperature before serving. This time allows the filling to thicken up. Cover leftovers tightly and store in the refrigerator for up to 5 days.
Notes
Make Ahead & Freezing Instructions: This a great pie to make 1 day in advance since it is so juicy – the filling will have time to set overnight. The pie crust dough can also be prepared ahead of time and stored in the refrigerator for up to 5 days or in the freezer for up to 3 months. Baked pie freezes well for up to 3 months. Thaw overnight in the refrigerator and allow to come to room temperature before serving. Prepared filling can be frozen up to 3 months, thaw overnight in the refrigerator before using.
