Wrap your 9-inch springform pan with 8-10 sheets of aluminum foil to prevent water from seeping in while baking.

In a food processor, pulse approximately 24 Biscoff cookies until they resemble fine crumbs.

In a mixing bowl, combine crushed cookies with melted butter and sugar. Press firmly into the bottom of the prepared springform pan.

Bake for 12 minutes at 350°F (175°C) until lightly golden, then let cool.

Blend softened cream cheese, sugar, and cornstarch on medium speed until smooth and fluffy for about 2-3 minutes.

Gradually add pumpkin puree, sour cream, pumpkin pie spice, and vanilla extract and mix until creamy.

Add eggs and egg yolks, mixing on low speed just until combined.

Pour the cheesecake filling over the cooled crust and smooth the top. Place in a larger roasting pan with boiling water halfway up the sides.

Bake at 325°F (160°C) for 1 hour.

Turn off the oven and crack the door ajar, allowing the cheesecake to cool for another hour.

Let it cool to room temperature before refrigerating for at least 8 hours or overnight.

Beat together softened butter until fluffy, then add softened cream cheese and mix until velvety.

Incorporate sifted powdered sugar slowly until smooth, ready for decorating.

Remove cheesecake from the springform pan, pipe frosting around the edges, and sprinkle crushed Biscoff cookies on top.

Slice and serve.