Crush biscuits to fine crumbs. Melt unsalted butter with microwave at 600W for 40-60 sec. Add the melted butter to the biscuits, and mix well.

Press the biscuit mixture into the bottom of the cake pan. Grease inside of the pan with butter. Let it sit in a fridge.

Make the cheesecake batter. Preheat your oven to 160℃ / 320 F. Smooth cream cheese with a spatula. Add granulated sugar and mix well. Mix until the roughness of the sugar disappears for 2-3 minutes.

Add an egg and use a whisk to stir well until smooth. Add whipping cream and stir well until smooth.

Add vanilla oil and stir well. Add lemon juice and rum, and stir well until smooth.

Sift cake flour over the mixture. Stir well until smooth. Transfer 120g / 4.2 oz (around 1/3 of the batter) into another bowl.

[ For Chocolate Batter ] Melt chocolate with a microwave at 600W for 1 minute. Add the chocolate to the transferred batter and stir well until smooth. Sift cocoa powder over and stir well until smooth. Add 2 tsp whipping cream and stir well until smooth.

Take the cake pan out from the fridge. Pour half of the white cheesecake batter into the pan and spread it. Use a spoon to put the chocolate batter over in some places. Next, put the white batter over in some places. Repeat it.

Use a spoon to stir slowly while drawing circles, create a marble pattern. Since the cheesecake bakes in a water bath, place the pan inside a larger pan or cover the pan with aluminum foil to prevent the water from seeping in during baking.

Pour plenty of 50℃ / 122 F hot water into a deep-sided container. (If you mix water and boiling water in the same ratio, it reaches about 50℃ / 122 F.) Place the cheesecake in hot water. Lower the oven to 150℃ / 302 F and bake for 35 minutes. After baking, keep the oven door closed, put it in for 15 minutes, and slowly cook it with residual heat.

Let it cool well and let it sit in a fridge overnight. The next day, warm the side of the pan with a hot steamed towel, melt the butter, and then remove it from the pan. Thank you!