Preheat your oven to 350°F and set out a standard pie pan. Place the Biscoff cookies in a food processor, drizzle in the melted butter, and process until the mixture resembles fine, sandy crumbs with no large pieces remaining. Tip the crumb mixture into the pie pan, then use the bottom of a measuring cup or glass to press it firmly and evenly across the base and up the sides to form a compact crust.
Transfer the crust to the oven and bake for about 8 minutes, just until it is lightly set and fragrant. Remove from the oven and allow it to cool completely to room temperature before adding any filling.
While the crust is baking, melt 1 cup of mini dark chocolate chips using a double boiler. Fill a small saucepan with a little water and bring it to a gentle simmer. Set a heatproof bowl over the pan, ensuring the bottom does not touch the water. Add the chocolate chips to the bowl and stir steadily until they are fully melted and smooth. Stir in the coconut oil until the mixture is glossy and fluid.
Once the crust has cooled, pour the melted chocolate into the shell. Use a spatula to spread it into an even layer over the base, making sure it reaches all the edges. Place the pie crust in the refrigerator until the chocolate layer has completely set and firmed up, ready for the filling.