Preheat your oven to 350°F (175°C) and wrap a 9-inch springform pan tightly with aluminum foil.

In a food processor, pulse the Biscoff cookies, sugar, and melted butter until finely crushed. Press into the bottom of the springform pan and bake for 12 minutes.

Let the crust cool while preparing the filling.

In a stand mixer, combine softened cream cheese with sugar and cornstarch, beating until smooth.

Gradually add pumpkin puree, sour cream, pumpkin pie spice, and vanilla, mixing until just incorporated.

Add eggs and egg yolks one at a time on low speed, mixing until just combined.

Pour the cheesecake batter into the cooled crust, place the springform pan in a larger roasting pan, and add boiling water around it.

Bake for 1 hour. Turn off the oven and crack the door open to cool slowly for another hour.

Remove the cheesecake from the oven and let it cool at room temperature for about an hour.

Cover and refrigerate for at least 8 hours or overnight.

In a mixing bowl, whip softened butter until pale and fluffy. Mix in cream cheese until combined.

Gradually sift in powdered sugar, blending until fluffy.

Remove the cheesecake from the springform pan and pipe frosting around the edges.

Optionally sprinkle crushed Biscoff cookies on top before serving.