I have made mini ice cream cakes before, but never a big cake. Part of the reason was I didn't have a springform pan. But now I do and it was very easy to put together.
First I started with crushed chocolate wafer cookies and added magic shell. I placed enough to cover the bottom of the springform pan and pressed the crushed cookies down. The pan went into the freezer while I waited for the chocolate ice cream to melt. As it was softening, I decided to mix it together with my standing mixer. This allowed the melted parts to be incorporated with the ice cream and made it easier to spread.
I spread the first layer onto the crushed cookie and sent it back to the freezer.
The next step was more crushed cookie mixture, more freezer time, and finally the softened vanilla layer. Again I used the standing mixer to prepare the ice cream.
We tried a couple stabilized whipped cream methods with no luck. In the morning I tried one more time with gelatin. I used cold water and gelatin, then used the microwave to dissolve it further in very small bursts. It cooled as I whipped the cream.
After adding the gelatin, the whipped cream looked different for me, but tasted ok. I placed it in the fridge while I took the cake out of the springform ring. After releasing the ring, I took a spatula warmed in hot water and gently cut around the cake edge.
I could probably use any kind of whipped cream to cover the cake as it freezes almost immediately. I wanted the use the stabilized whipped cream to pipe on the cake and it seemed to work pretty well. Once I got going on the frosting, I did return it to the freezer between steps, but generally worked quickly. I had to let the cake thaw a little in order to press the m&m's into the cake. I wish I had spaced the m&m's a bit better, I'll know for next time.
I had enough whipped cream frosting to cover the cake with a thin layer and color some purple and decorate. There's a bit of white saved for any cake mishaps too.
To preserve this cake for a week in the freezer, I needed some sort of box. The base of my cake holder is too big to fit in my freezer. What I ended up doing was placing the cake on a 10" cake board. Then I put two pieces of aluminum foil spread out on a dinner plate. I placed the cake on the plate, then put the cake holder cover on top. The cover just fit over the bottom plate edge. Then I took the excess foil and wrapped it over the cover edges. Hopefully that will be protected well in the freezer until the party!