Preheat your oven to 350°F (175°C).

In a food processor, pulse Biscoff cookies into fine crumbs, then combine with melted butter and sugar in a mixing bowl.

Press the mixture firmly into the bottom and slightly up the sides of a springform pan, creating a solid crust.

Bake the crust for 10 minutes, then remove and let cool completely.

In a stand mixer, beat cream cheese, corn starch, and granulated sugar until smooth. Incorporate Biscoff cookie butter, vanilla extract, and sour cream.

With the mixer on low, add eggs and egg yolks one at a time until just combined.

Pour the cheesecake filling into the cooled crust and smooth the top.

Place the cheesecake pan into a larger roasting pan and add hot water halfway up the sides of the cheesecake pan.

Bake the cheesecake for 1 hour until edges are set but center is slightly jiggly.

Turn off the oven and crack the door open, allowing the cheesecake to cool inside for an hour.

Loosen the edges with a knife and let the cheesecake come to room temperature, then chill in the refrigerator for at least 8 hours.

Before serving, drizzle melted Biscoff cookie butter on top and add whipped cream and cookie crumbs if desired.