Place the hazelnuts and granulated sugar in a food processor, and pulse until you have a coarse, sandy mixture. Don't go too crazy, or you'll end up with hazelnut butter!

Add the eggs, unsalted butter, hazelnut extract, vanilla extract, and a pinch of salt. It will be the consistency of pastry cream. Store in the fridge until you're ready to use.

Preheat the oven to 400°F. Line two sheet pans with parchment paper. Set aside.

Roll out your pie dough in two batches until they are 1/8'' thick and 12'' in diameter. After you roll out the dough, refrigerate on the prepared sheet pans until you're ready to assemble. (If you are going the store-bought route, just unroll the pie dough right before you're ready to assemble).

Next, gently fold the blueberries with the sugar, flour, lemon zest, lemon juice, vanilla extract, hawaij (or apple pie spice), cinnamon, and salt. Set aside.

Spread half the frangipane on one of the pie crusts, leaving a 1'' border. Spoon half of the blueberry mixture over the frangipane, leaving another 1/2'' border. Then, fold the edges of the dough over the berries, gently pressing to make sure the folds stick. Repeat with the remaining ingredients so you have two galettes.

Brush the edges of the dough with egg wash and sprinkle with demerara sugar. Bake at 400°F for 45-50 minutes, until the filling is bubbling and the crust is golden-brown. Serve warm with ice cream!