Preheat oven 325 degrees. Place a large roasting pan on the lower rack in oven. Boil some water. Spray a 9 inch sringform pan and line bottom with parchment paper. Wrap a double layer of foil around bottom and up sides of pan so water won't get in. This will ensure that the cheesecake won't crack.
2Blend cream cheese until creamy. Add sugar and salt. Blend in eggs one at a time. Mix in sour cream, heavy cream, and vanilla.
3Pour batter into pan. Place pan in roasting pan. carefully pour boiling water around pan and about 1 inch up sides. Bake 45 minutes or until set. Let it cool for an hour and then place the pan in the freezer for 24 hours.
Mix flour, cocoa powder, and salt set aside. Combine oil and sugar add eggs 1 at a time. Mixing well. In small bowl combine vinegar and baking soda until soda is dissolved.
5Add vinegar to oil mixture along with the buttermilk and food coloring. Add dry ingredients. Mix well
6Generously spray two 9 inch round pans and pour prepared batter into pans. Bake at 350 degrees for 30 min. Let cool completely.
Beat cream cheese and butter until smooth. Add marshmellow cream and mix well. Add powdered sugar and food coloring if using. Refrigerate until needed.
8To assemble cake
Place one layer in center of plate. Remove cheesecake from freezer trimming if needed. Lay on first layer. Top with 2nd layer and Frost. Refrigerate