For the Fresh Blueberry Jam

• In a small saucepan, combine 1 1/2 C of the fresh blueberries, the sugar, and the lemon juice and zest.
• Cook over medium heat for 5-7 minutes, until most of the blueberries have burst and have formed a sauce.
• Stir in a cornstarch slurry (2 tsp cornstarch 3 tsp water) and bring to a low boil for 1 minute or until jam has thickened enough to coat the back of a wooden spoon. Fold in the remaining 1/2 C fresh blueberries.
• Allow to cool completely. The jam will continue to thicken as it cools.

For the Lemon Shortbread Crust

• Preheat oven to 350 and line a 9X9 pan with parchment and a light spray of nonstick.
• In the bowl of a stand mixer with the paddle attachment, beat the butter and sugars for 3 minutes.
• Add in the vanilla, lemon extract paste, and lemon zest. Mix to combine.
• Add in the flour and salt. Mix until the dough comes together and pulls away from the sides of the bowl – about 1-2 minutes.
• Press 2/3 of the dough into an even layer into the prepared baking pan.
• Pour the cooled blueberry jam over the crust and spread out evenly using an offset spatula.
• Top with remaining shortbread crust. Use your fingers to press pieces of the crust into flat discs and place randomly over the top.
• Bake at 350 for 40-45 minutes, until blueberry jam starts to bubble around the edges and shortbread is lightly golden brown. 
• Top with extra lemon zest optional.
• Let cool completely, then slice and serve.