The ice cream needs a minimum of 6-8 hours to set in the freezer, so it is essential to plan.
Grease the bottom and sides of one 8-inch or 9-inch pan and line with parchment paper. Set aside.
In a bowl of a standing mixer, fitted with the whisk attachment, pour the heavy cream and whip, starting on low speed and gradually increasing to high speed until the cream is thick.
Pour in the sweetened condensed milk and gently fold to incorporate.
Fold in the ground Oreos.
Pour the mixture into the prepared pan and place in the freezer to set for a minimum of 6-8 hours or preferably overnight.
To Make The Frosting
Pour the heavy cream into a chilled bowl of a standing mixer fitted with the whisk attachment. Add the powdered sugar and dry milk powder.
Whip on low speed, gradually increasing speed to high until the cream is thick and stabilized.
Preparing the Toppings
Melt the chocolate, then add the oil, and stir until smooth. The chocolate should be soft and warm but not hot.
Line a bowl with a paper towel and gently place the maraschino cherries. Gently and slowly swirl the bowl to remove and access liquids.
Assembling
Have the cake, ice cream, and frosting ready with your serving plate, a turn table (if using), and an offset spatula (if using).
Place one cake layer on your serving plate, then top it with the ice cream, then top with the second layer of cake. (For an easy release, dip the bottom of the pan into a large bowl of water for 2 seconds.)
Frost with the stabilized whipped cream, then place it back in the freezer to firm up for about 30-45 minutes.
Remove from the freezer and use a spoon to drizzle the ganache.
Fill a piping bag fitted with a large rose tip (I used Wilton 1M) with the remaining whipped cream and pipe eight rosettes on top of the cake.
Sprinkle the top of the cake with the crushed Oreos and top each rosette with maraschino cherries.
Freeze until serving.