Wrap a 9-inch springform pan in aluminum foil to prevent water seeping in. Place it inside a larger roasting pan.

Preheat your oven to 350°F (175°C).

In a medium bowl, mix softened butter, brown sugar, all-purpose flour, pumpkin pie spice, and salt until crumbly. Refrigerate for 30 minutes.

Pulse Biscoff cookies in a food processor to make crumbs. Combine with melted butter and sugar. Press into the bottom of the springform pan and bake for 15 minutes.

Beat cream cheese until smooth. Gradually add brown sugar and cornstarch. Mix in pumpkin purée, sour cream, and pumpkin pie spice, then add eggs one at a time while mixing on low.

Pour half the cheesecake batter into the crust. Add the spiced brown sugar filling, then top with remaining batter and streusel. Bake for 1.5 hours in the water bath.

Let the cheesecake cool in the oven with the door slightly ajar for 1 hour, then transfer to a wire rack to cool before refrigerating overnight.

Whip heavy cream to soft peaks, adding powdered sugar and whipping to stiff peaks. Pipe around the cheesecake for serving.

Carefully slice into wedges, and drizzle with caramel sauce or sprinkle with nutmeg before serving.