In a liquid measuring cup, add ½ cup of very cold water and stir in the lemon juice. Place in refrigerator until ready to use.
In a large mixing bowl, whisk together flour, salt and granulated sugar. Add in your cubes of butter and shortening. Lightly toss to evenly coat all of the cubes in flour.
Using a pastry cutter or your fingers, work the butter / shortening into the flour mixture until most of the butter chunks are the size of peas, with some larger almond-sizes chunks remaining. The rest of the mixture should look like coarse sand.
Drizzle half of the ice water & lemon juice mixture over the dry ingredients and gently toss with your hands or a spatula. Drizzle the remaining half of the wet ingredients and gently stir with the spatula until a ragged dough forms.
Tip: Avoid the temptation to add more water as this can run the risk of making a chewy dough as opposed to the more desired flaky dough.
Turn the dough out onto a lightly floured work surface & divide into 2 equal portions. Shape the doughs into rectangles about 1 inch thick and wrap with plastic wrap. Refrigerate for at least 1 hour or make ahead and refrigerate for up to 2 days.
Make the egg wash:
In a small bowl whisk together egg, milk and sugar; place in refrigerator until ready to use.
Strawberry Rhubarb Filling:
Heat 1 tbsp of the butter in a large sauté pan over medium-high heat. Sauté the chopped rhubarb w/ 1 tbsp of the brown sugar until it softens slightly, about 5 minutes.
Transfer the rhubarb to a large bowl, sprinkle with the lemon juice and allow it to cool completely to room temperature. Place in the refrigerator if needed.
Meanwhile, in a medium bowl, whisk together the sugars, flour, cornstarch, cinnamon, ginger and lemon zest.
After 1 hour, use a slotted spoon to transfer the macerated strawberries into the bowl with your cooled rhubarb, leaving behind any excess juices.
Assembly
Next, remove your chilled pie dough disks from the fridge & lightly flour a cool, dry work surface. Unwrap one disk and lightly flour its surface. Use a rolling pin to roll the dough into a ¼ inch thick rough rectangular base for your pie; Lift the crust onto a sheet pan lined with parchment paper.
Next roll the remaining pie dough in the same fashion as the first, into a ¼ inch thick rough rectangle. Set aside.
Sprinkle the base of the pie dough, with the almond meal - (this will help to absorb any excess juices from your filling and prevent a soggy pie crust)
Next finish preparing your filling; Add the strawberries to your sugar mixture. Stir in rhubarb, and vanilla; Stir gently with a spatula until evenly coated.
Pour the filling onto the pie base on the sheet pan to evenly distribute among crust, leaving a 1 inch border. Dot the filling with chunks of the remaining 1 tbsp of chilled butter.
Brush the edges of the pie base with egg wash. Gently lift the other pie dough on top of the filling and use a fork to press around the edges. Cut off any rough or excess dough around the edges if desired.
Brush the top of the pie evenly with the egg wash. Sprinkle with coarse sugar and cut a few slits in the pie for steam release while baking.
Place pie on a baking sheet to prevent bubbly filling from falling to the bottom of your oven and bake in the lower third of the oven at 375 degrees 30 – 35 minutes or until the crust is golden brown and the filling is bubbling.
Remove from oven and allow to cool for 10 – 15 minutes before glazing.
Lemon Strawberry Glaze
While your pie cools, make your glaze.
Place all ingredients in a bowl and whisk together until smooth and creamy. You want it to be thick but still pourable. If your glaze is too runny, add in a bit more icing sugar 1 tbsp at a time. If your glaze is too thick add in more water 1 tbsp at a time.
Use a spoon to glaze the pie & sprinkle with sprinkles if desired. Allow to set for 10-15 minutes before slicing. Enjoy!