Begin by crushing approximately 20 Biscoff cookies into fine crumbs. Combine with melted butter until the texture resembles wet sand. Press mixture into the tart pan to create the crust.

Heat 1 cup of heavy cream until it simmers. Pour over 8 ounces of chopped dark chocolate and let sit for 5 minutes, then stir until smooth to create ganache.

Spread a layer of cookie butter over the crust, then pour the ganache on top, smoothing it out for presentation.

Cover the tart with plastic wrap and refrigerate for at least 4 hours or overnight.

Once set, lift the tart from the pan, slice into wedges, and serve chilled, optionally garnished with cocoa powder or whipped cream.