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

In a food processor, pulse Biscoff cookies, then mix with melted butter and sugar until sandy. Press into the springform pan and bake for 12 minutes.

In a stand mixer, blend softened cream cheese, sugar, and cornstarch until smooth. Add pumpkin puree, sour cream, pumpkin pie spice, and vanilla, mixing gently.

Incorporate eggs and yolks one at a time on low speed. Pour filling over cooled crust.

Place cheesecake pan into a larger roasting pan and pour boiling water until it reaches 1.5 inches up the sides.

Bake for 1 hour until edges are set. Turn off oven and cool cheesecake inside for another hour.

Let cheesecake cool to room temperature, cover with plastic wrap, and chill in refrigerator for at least 8 hours.

For frosting, beat softened butter until fluffy. Gradually add cold cream cheese and powdered sugar until combined.

Once chilled, remove cheesecake from pan, pipe frosting, and optionally sprinkle with crushed Biscoff cookies.