In a food processor, add the crushed Biscoff cookies and melted butter, mixing until combined. Press this mixture firmly into a tart pan, ensuring an even layer across the bottom and up the sides. Chill the crust in the refrigerator for about 30 minutes.

In a small saucepan, heat the heavy cream over medium heat until it just begins to bubble. Remove from heat and pour the hot cream over roughly chopped dark chocolate in a bowl. Let this mixture sit for 5 minutes to soften the chocolate, then stir until smooth and glossy.

Once the ganache is smooth, add the Biscoff cookie butter to the mixture. Stir continuously until well incorporated.

Take the chilled crust from the refrigerator and pour the luscious ganache into the tart shell. Gently spread the ganache with a spatula, smoothing the top for an even finish.

Cover the Chocolate Biscoff Tart with plastic wrap and place it back in the refrigerator. Allow it to chill for at least 2 hours, or until the ganache is set and firm.