Preheat oven to 350°F. Wrap the outside of a 9-inch springform pan with heavy-duty foil.
Mix Biscoff crumbs, melted butter, brown sugar, and salt until evenly moistened.
Press mixture into the bottom and 1 inch up the sides of the pan.
Bake for 8–10 minutes. Remove from oven and reduce temperature to 325°F.
Place a large roasting pan in the oven and fill with about 1 inch of hot water.
Beat cream cheese until smooth, about 1 1/2 minutes. Scrape bowl.
Add sugar and lemon zest. Beat 1 minute.
Add eggs one at a time, mixing and scraping between each addition.
Add lemon juice, vanilla, sour cream, flour, and 1/2 cup heavy cream. Mix until just combined.
Stir in melted white chocolate by hand.
Pour filling into cooled crust and gently shake to level.
Place springform pan in the water bath. Bake for 85–95 minutes, until edges are puffed and center slightly jiggles.
Turn oven off, crack door, and let cheesecake cool in oven for 1 hour.
Remove and cool completely on a wire rack for 1 1/2–2 hours.
Cover and refrigerate overnight.
Whip 1 cup heavy cream to soft peaks. Fold in lemon curd. Spread over chilled cheesecake.
Whip cream, powdered sugar, vanilla, and cornstarch to stiff peaks. Pipe or dollop around edges.