In a food processor, process hazelnuts, cookies, light brown sugar, and melted butter until ingredients are fully incorporated.
Press crust mixture into the bottom of a 9-inch springform pan, and a little bit up the sides. Just for show (but also to keep the chocolate from spilling over).
Bake at 325 degrees for about 8-10 minutes, just until the crust is slightly darker in color.
Remove from oven and allow to cool slightly before filling.
Make the Chocolate Filling
In a double boiler or a glass bowl placed over a small pot of water (so the water is just touching the bottom of the bowl), bring water to a low boil over medium heat. Add chocolate chips and whisk until chocolate just begins to melt a little, and then slowly add almond milk. Turn off heat and whisk together chocolate and almond milk until the mixture is smooth and all the chocolate is fully melted. Remove bowl, place on heatproof counter top, and set aside to cool slightly.
Add avocado, cocoa powder, vanilla extract, and agave nectar (or honey) to a food processor**. Add melted chocolate. Process until the mixture is blended and smooth.
Make the optional topping
In a food processor, blend ¼ cup hazelnuts with 3 Biscoff cookies.
Sprinkle over the pie for additional hazelnut yumminess.
Notes
* I use Enjoy Life dairy-free chips but you can use any dairy-free chocolate. No need to be dairy-free? Use regular chocolate chips!
**No need to wash out the food processor in between uses here. In fact, I recommend NOT doing so because the yummy remaining bits of Biscoff cookies and hazelnuts used to make the crust add even more deliciousness to the filling!