Preheat your oven to 350 degrees Fahrenheit. Crush the Biscoff cookies into fine crumbs using a food processor or by placing them in a sealed bag and rolling them with a rolling pin. In a medium bowl, mix the crumbs with the melted butter until the mixture feels like wet sand.
Press the buttery cookie crumbs firmly into the bottom and up the sides of a 9 inch pie dish. Use the bottom of a measuring cup to ensure the crust is even and tightly packed. Bake the crust for 8 to 10 minutes, then remove it from the oven and let it cool slightly while you prepare the filling.
In a large mixing bowl, whisk together the pumpkin puree, sweetened condensed milk, and eggs until the mixture is completely smooth. Stir in the pumpkin pie spice, alcohol-free vanilla extract, and salt. Make sure there are no streaks of egg remaining to ensure a perfectly uniform texture.
Pour the pumpkin mixture into the pre-baked Biscoff crust. Carefully place the pie back into the oven and bake for 40 to 50 minutes. The edges should be set and slightly puffed, while the center should still have a slight jiggle when you gently shake the pan.
Remove the pie from the oven and let it cool completely on a wire rack for at least 2 hours. This step is crucial because the pie continues to set as it cools. For the best results, refrigerate the pie for another 4 hours or overnight before slicing and serving.
