using a cake pan the same size as the cake press parchment paper into every side, fill with the first ice cream if you want any type of filling do it now, before you press the cake down
Press the cake down into the ice cream. Freeze overnight
Pull the cake out and put it on a cake board, peel back the parchment paper. frost with the softened vanilla ice cream. Refreeze.
Decorate with buttercream however you like! And refreeze. put out about 10 mins before serving, cut with a warm knife.