Preheat your oven to 180°C (350°F).

Set aside 1/4 of your pastry dough for spooky shapes and refrigerate it. Roll out the remaining dough, fit it into a flan tin, and freeze for 30 minutes.

In a mixing bowl, combine half of the frozen mixed berries, sugar, lemon juice, and the corn flour slurry. Cook over medium heat for about 10 minutes until bubbling, stirring often. Fold in the remaining berries and allow to cool.

Carefully fill your chilled pastry base with the prepared berry mixture, distributing it evenly.

Roll out reserved pastry dough and cut out fun spooky shapes. Place these on top of your filled pie and seal the edges.

Brush the decorated pie with an egg wash. Bake in the preheated oven for 40 minutes or until the crust is golden brown.

Allow the pie to cool slightly before slicing. Serve it warm with ice cream or enjoy on its own.