Place the 9 ounces (255 g) of Biscoff cookies in a food processor and pulse until finely crushed. The crumbs should resemble coarse sand, with no large pieces remaining. Alternatively, crush the cookies in a sealed zip-top bag using a rolling pin.

Combine the cookie crumbs with 6 tablespoons (85 g) melted butter. Stir until evenly moistened. The mixture should resemble damp sand and hold together when squeezed. Transfer to a 9-inch (23 cm) springform pan. Press firmly and evenly across the bottom using the base of a measuring cup or glass. Refrigerate for 30 minutes while preparing the filling.

Place the softened cream cheese in a large mixing bowl. Beat with an electric mixer on medium speed for 1–2 minutes until smooth and free of lumps. Add the 1 cup (250 g) Biscoff spread and continue mixing until fully incorporated. Scrape the sides and bottom of the bowl to prevent streaks of unmixed cream cheese.

Add the ¾ cup (90 g) sifted powdered sugar and 1 teaspoon (5 ml) vanilla extract. Mix on low speed initially, then increase to medium until the filling is thick, smooth, and evenly colored. It should have a soft caramel-beige appearance without visible sugar or cream cheese lumps.

In a separate chilled mixing bowl, beat the 1¼ cups (300 ml) cold heavy whipping cream on medium-high speed until stiff peaks form, approximately 2–4 minutes depending on the mixer. The whipped cream should hold its shape when the beaters are lifted, with peaks that stand upright. Stop before the mixture becomes grainy or begins separating.

Add about one-third of the whipped cream to the Biscoff cream cheese mixture. Fold gently with a silicone spatula to loosen the filling. Add the remaining whipped cream in two additions, folding until no white streaks remain. The finished mixture should be thick, fluffy, and smooth. Avoid vigorous stirring, which can deflate the whipped cream and make the cheesecake denser.

Remove the chilled crust from the refrigerator: Spoon the cheesecake filling over the base and spread it evenly with an offset spatula. Gently smooth the surface, pushing the filling toward the edges to eliminate large air pockets. The filling should hold soft ridges rather than flow like liquid.

Warm the ½ cup (125 g) Biscoff spread in a microwave-safe bowl in 10-second intervals, stirring between each interval, until fluid and pourable. Alternatively, warm it gently in a small saucepan over low heat. Allow the spread to cool slightly until just warm, not hot. Pour it over the chilled cheesecake and gently tilt the pan or use an offset spatula to create an even layer.

Return the cheesecake to the refrigerator for at least 2 hours, allowing the topping to firm up and the filling to finish setting. Just before serving, sprinkle the optional 4 crushed Biscoff cookies around the edge. Arrange the optional 4 whole cookies on top for decoration. Adding the cookies close to serving helps preserve their crunch.

Run a thin knife around the inside edge of the springform pan, then carefully release the ring. Slice the chilled cheesecake into 12 portions using a sharp knife dipped in hot water and wiped dry between cuts. Serve cold for the cleanest slices and the firmest, creamiest texture.