Preheat the oven to 350 degrees Fahrenheit. Take the mixing bowl and whipping attachment for the stand mixer and stick them in the freezer.
Start by making the blueberry filling.
In a wide saute pan or pot, add in the blueberries, maple syrup, lemon juice, lemon zest, and water over medium heat. Let cook for 25-30 minutes, stirring occasionally, until the mixture has thickened and the liquid doesn't easily drip off a metal spoon. Set aside to cool completely.
While the jam is cooking, start on the crust!
In a food processor, pulse the graham crackers until crumbs are formed, then add in the walnuts, salt, cinnamon, and sugar. Continue to process until the crumbs are finely ground. Add in the melted butter and pulse another 30 seconds, stopping to scrape the sides if necessary (if using pre-crushed graham cracker crumbs, add them in with the walnuts and continue from there).
Add the mixture to an 8-inch pie plate and using your fingers, press the mixture into the plate and up the sides to form a crust. Bake in the oven for 8-12 minutes, until golden brown. Be careful not to burn it!
Take the crust out of the oven and set aside to cool.
Once the crust and the jam are both cooled down, start on the mascarpone cream.
Take the bowl and whipping attachment out of the freezer and place them on the stand mixer. Do this right before you're ready to make the mascarpone cream. The colder everything is, the better!
Add the heavy cream to the mixing bowl and whip at medium speed until the cream starts forming into a thickened, whipped deliciousness. Add in the vanilla extract and let it blend in. Sprinkle in the powdered sugar and continue to whip until stiff peaks are formed.
Turn off the mixer and switch out the whipping attachment with a flat beater, scraping all the cream from the ship attachment back into the mixing bowl.
On low speed, slowly add in the mascarone cheese 1-2 tablespoons at a time. Turn off mixer and scrape the paddle.
Phew, lots of steps! Almost done. Time to assemble the delicious pie!
Add the blueberry jam to the pie crust and spread it out evenly (do this carefully as the crust might still be a little crumbly; it will soften once it settles in the fridge).
Top with the mascarpone cream and spread evenly.
Top with the fresh blueberries and place the pie in the fridge for at least 3 hours.