Instructions:
- Preheat oven to 325°F (160°C). Wrap the exterior of a 9-inch springform pan securely in heavy-duty aluminium foil (twice) to prepare for the water bath.
- Make the Crust: Combine graham cracker crumbs, ¼ cup sugar, and melted butter. Press the mixture firmly into the bottom and slightly up the sides of the prepared springform pan. Bake for 10 minutes, then let cool slightly.
- Prepare the Water Bath (Bain-Marie): Place the foil-wrapped springform pan inside a large roasting pan.
- Mix the Filling: Beat the room temperature cream cheese until perfectly smooth. Gradually beat in 1 cup of sugar. Add sour cream, vanilla, and lemon zest. Beat in the eggs one at a time, mixing just until combined after each addition. Do not overmix!
- Bake: Pour the filling over the cooled crust. Carefully place the roasting pan onto the oven rack. Pour boiling water into the roasting pan until it reaches halfway up the side of the springform pan. Bake for 60–75 minutes, or until the edges are set but the center jiggles slightly.
- Cooling Protocol: Turn off the oven, crack the door open slightly, and let the cheesecake cool inside the oven for 1 hour to prevent cracking. Remove the cheesecake from the water bath, remove the foil, and cool completely on a wire rack.
- Chill: Cover the completely cooled cheesecake and refrigerate for a minimum of 6 hours, preferably overnight.
- Whip & Top: Once fully chilled, spread the marshmallow fluff evenly over the top surface. Use a kitchen torch to carefully toast the marshmallow until it achieves a lovely, deep golden-brown char.
- Serve: Carefully release the springform side and slice the Marshmallow Whip Cheesecake to serve.