Finely crush about 250g of Biscoff cookies in a food processor until they resemble sand. In a mixing bowl, combine the crushed cookies with 100g of melted unsalted butter.

Press the mixture into the bottom and up the sides of a 9-inch tart pan.

In a small saucepan, heat 200ml of heavy cream over medium heat until it simmers. Remove from heat and pour it over 200g of chopped dark chocolate. Let sit for 3–5 minutes, then stir until smooth.

Stir in 100g of Biscoff spread into the ganache, mixing until fully blended.

Pour the ganache mixture into the prepared Biscoff crust, spreading it evenly.

Chill in the refrigerator for at least 4 hours, until set.

Slice and serve chilled, optionally garnished with whipped cream or chocolate shavings.