In a large mixing bowl, combine the flour, salt, and sugar.

Add the cold, cubed butter into the flour mixture and mix until it resembles coarse crumbs.

Gradually add ice water, one tablespoon at a time, until the dough begins to come together.

Knead the dough gently and divide it into two balls, flatten into discs, and wrap in plastic wrap.

Chill in the refrigerator for at least 1 hour.

Preheat the oven to 375°F (190°C).

Remove one disc of dough from the refrigerator and roll it out into a circle.

Press the dough into the pan and trim into a heart shape.

In a large bowl, combine the mixed berries, granulated sugar, cornstarch, lemon juice, and vanilla extract.

Gently stir to coat the berries and allow to sit for a few minutes.

Pour the berry filling into the prepped crust.

Roll out the second disc of dough and cut into strips or create a heart shape.

Arrange over the filling and brush with egg wash, sprinkle with sugar if desired.

Bake for 45-50 minutes or until golden brown and bubbling.

Let cool for at least 30 minutes before serving.