Chill a nine-inch springform pan in the freezer. This will keep the ice cream from melting during cake assembly.
Preheat oven to 350°. While heating, pulse Oreo cookies in a food processor several times.
Put the cookie crumbs on a parchment-lined baking sheet and spread them evenly. Remove from oven after 10 minutes and cool fully.
Pour over semisweet chocolate chips in a medium glass bowl after removing from heat. Mix heavy cream and chocolate until smooth.
Stir corn syrup and vanilla essence into the chocolate-cream mixture until glossy and totally integrated. Allow the ganache to cool fully
Spoon chocolate ice cream into the center of the vanilla-ice cream-lined cake pan after the "wall" has firmed.
Next, Spread ganache with an offset spatula and top with cold cookie crumbles. Gently massage the crumbles into an equal layer.