Preheat your oven to 350°F (175°C). In a food processor, pulse the Biscoff cookies into fine crumbs, then combine them with melted butter and sugar until well mixed. Press this crumb mixture firmly into the bottom of a 9-inch springform pan to form an even crust. Bake the crust for 10 minutes, then take it out and allow it to cool while you prepare the filling.

In a large stand mixer, beat the room temperature cream cheese until creamy and smooth. Gradually add in the corn starch and granulated sugar, mixing until fully combined. Next, blend in the Biscoff cookie butter, vanilla extract, and sour cream until the mixture is well incorporated, creating a rich and velvety filling.

With the mixer on low speed, add the eggs and egg yolks one at a time, mixing gently to avoid overmixing. Once all the eggs are added, your Biscoff cheesecake filling should be smooth and creamy.

Pour the cheesecake filling over your cooled crust, smoothing the top with a spatula. Place the springform pan inside a roasting pan filled with hot water for a water bath, which helps prevent cracking. Bake in the preheated oven for 1 hour. Turn off the oven and let it cool inside with the door ajar for an additional hour.

After cooling at room temperature, let the cheesecake chill completely in the refrigerator for at least 8 hours, or overnight if possible.

Once chilled, gently pour the melted Biscoff cookie butter over the top of the cheesecake. Use a spatula to spread it evenly. Chill the cheesecake again for 20 minutes before slicing.