Preheat oven to 350F/180C. Prepare a 8 inch/20 cm springform non stick cake pan and line the base with parchment. Wrap the cake pan all round in 3 layers of aluminum foil.
Place biscoff cookies,sugar and jaggery in a food processor fitted with a metal blade. Whiz to crumbs. Add ghee and pulse to combine. Press the cookie crumbs to the base of prepared pan. Keep ready.
Put water to boil in a kettle or over stove .Place cream cheese in a stand mixer fitted with paddle attachment. Beat for 2 minutes until the cheese is smooth.
Add the jaggery and beat for 1 minute. Scrape down the sides as needed.
Add the sour cream and heavy cream. Beat for 1 minute.
Add the eggs one at a time, beating total for 1 minute. Scrape down the sides as needed. Add in the cornstarch and lemon juice. Beat to combine .
Strain the cheese filling. This step is optional but recommended.
Pour the filling over the crust. Smoothen the top using a flat spatula. Tap gently to get rid of air bubbles.
Place the cake pan in a large roasting pan. Add enough boiling water till halfway up the sides of the pan.
Reduce the oven to 300F/150C. Carefully place the roasting pan in the oven and bake for 1 hour and 40 minutes or until the sides are set and the center is wiggly. Dont peek.
Turn the oven off and let cool for 30 minutes. Dont peek. Slightly pop open the door of the oven using a wooden spoon and let the cake cool for another 30 minutes.
Remove the cake from the oven and cool it to room temperature.Chill overnight or for atleast 6 hours.
Unmould the cake and seve topped with whipped cream and nuts.