Step 1

Preheat oven to 375 degrees.

Step 2

In a small bowl, whisk together the egg yolk and cream. Set aside.

Step 3

In a medium bowl, toss together the blueberries, 1-2 Tablespoons sugar, 1 Tablespoon arrowroot, 1 teaspoon lemon juice, and cassis, if using, until no arrowroot is visible. Set aside.

Step 4

In a large bowl, toss together the strawberries, 4-6 Tablespoons sugar, 3 Tablespoons arrowroot, 1 Tablespoon lemon juice, vanilla, and salt, until no arrowroot is visible. Set aside.

Step 5

Roll the larger disk of pie dough on a lightly floured countertop, regularly checking to make sure disk is not sticking to counter. You want to roll the dough to exceed the border of a 15 x 10-inch baking sheet by 1½ inches on all sides. Fold the dough and fit in and up the sides of the baking sheet. If you have to patch some pieces of dough in there, go for it. Trim the edges with a sharp knife and transfer the baking sheet into the refrigerator.

Step 6

Take the second disk of dough and roll it out in the same manner, but keeping in mind you'll need the following 1-inch wide strips: 3 strips 15½ inches long + 4 strips 10½ inches long + dough scraps you'll roll out to cut stars.

Step 7

Take 1 short strip and create a reverse "L" and make a square in the upper left corner of the baking sheet. Fill this with the blueberry mixture.

Step 8

Fill the remainder of the shell with the strawberry mixture.

Step 9

Take the 3 long strips and arrange across the lower half of the baking sheet. Take the 3 remaining shorter strips and arrange across the upper portion of the baking sheet. You want the "stripes" to be equi-distant from each other.

Step 10

Take the leftover scraps of dough and using a very small, 1-inch star cutter, make as many stars as you can that will fit over the blueberry section. Brush the stars with reserved egg wash and place across the blueberry filling.

Step 11

Carefully brush the stripes with egg wash. Bake until crust is golden brown and filling is bubbling, about 45-55 minutes. Transfer pie to a cooling rack and allow filling to set, at least 45 minutes. Serve warm or at room temperature. I make this pie the day before and keep it covered at room temperature.