• Preheat the oven to 400 °F.
• Roll the pie into a 12-inch circle.
• Carefully transfer the pie dough to a 9-inch pie dish.
• Poke the dough with a fork 5-6 times on the bottom and side.
• Place the pie dish into the fridge or freezer until ready to fill with the blueberry mixture.

Make The Crumble

• In a mixing bowl, add the flour, sugar, and oats. Mix well.
• Add the butter and mix until you have a crumbly texture, similar to wet sand.
• Set aside.

Blueberry Pie Filling

• In a large mixing bowl, add the blueberries and sprinkle the sugar, brown sugar, lemon zest, and vanilla extract over the blueberries. Mix well so all blueberries are coated with the sugars.
• Sprinkle the cornstarch over the blueberries. Gently mix. I used 2 large spoons and tossed like a salad. The blueberries will look dry, and you will have a dry mixture at the bottom of the bowl.
• Pour the blueberry mixture into the pie dish. Ensure that you add all the dry mixture to the pie.
• Spread the blueberries evenly.
• Add the crumble over the blueberries.
• Place the pie dish into a cookie sheet on the lower rack in the oven.
• Bake in the preheated oven for 15 minutes.
• Reduce oven temperature to 375 °F and bake for 45-50 minutes. Check the pie after 30 minutes. If it is browning too fast, loosely cover with aluminium foil.
• The pie will be ready when the crumble is golden and the blueberry mixture MUST BE BUBBLING HARD.
• Take out of the oven and cool completely (minimum 4-6 hours, but highly recommend overnight).