In a large mixing bowl, whisk together 2 ½ cups of all-purpose flour and 1 teaspoon of salt.

Cut in 1 cup of cold, cubed butter using a pastry cutter until the mixture resembles coarse crumbs.

In a separate bowl, whisk together 1 large egg yolk and 5 tablespoons of 2% milk until well combined.

Gradually pour the wet mixture into the flour and butter blend, stirring until a dough forms.

Divide the dough into two equal portions, flattening each into a disk. Wrap them in plastic wrap and refrigerate for at least 1 hour.

Preheat your oven to 375°F (190°C) while you roll out the larger portion of your chilled dough.

On a lightly floured surface, roll out the larger disk of dough into an 18x13-inch rectangle and transfer it to an ungreased baking pan.

In a large bowl, combine ¾ cup of sugar and 3 tablespoons of cornstarch. Fold in 2 cups of fresh or thawed raspberries and 2 cups of chopped rhubarb until well-coated.

Pour the filling into the prepared crust, spreading it evenly within the crust borders.

Roll out the second disk of dough into a rectangle that fits your pan size. Place it over the fruit filling and seal the edges by crimping.

Bake for 45 to 55 minutes, or until the crust is golden brown and the filling is bubbling.

Allow the pie to cool completely in the pan on a wire rack before icing.

Drizzle icing made from 1 cup of confectioners' sugar and 1 teaspoon of vanilla extract mixed with a bit of milk over the cooled pie.

Slice into generous pieces and serve warm or at room temperature, optionally with ice cream or whipped cream.