1. Make the cookie crust - In the bowl of a food processor, add the entire Oreo cookies (no need to remove the cream filling) and pulse into fine crumbs. Add the milk and melted butter and blend until well combined. Press mixture into the bottom and sides of a 6" springform pan. Place in freezer for about 30 minutes-1 hour to set.

2. Take out the chocolate ice cream to soften (about 20-30 minutes) and stir occasionally until smooth and spreadable. Stir in half of the crushed Oreo cookies.

3. Spread chocolate ice cream evenly over the cookie crust using an offset spatula if needed. Top with crushed Tim Tam biscuits if desired.
4. Place in freezer to harden for about 20 minutes while taking out the container of vanilla ice cream to soften. Once softened, mix in the other half of the crushed Oreo cookies.
5. Spread evenly to make the top layer.
6. Return to freezer and allow to set for at least 2-3 hours, or ideally overnight.
7. When ready to serve, let the cake sit at room temperature for about 3-5 minutes, and run a knife around the inside of the cake pan. Open the springform mold gently; it should release easily from the slightly melted cake..
8. Before serving, spread a layer of whipped cream frosting over the ice cream, pipe on rosettes if desired and arrange Oreo cookies in a circular design. Crumble any leftover cookie crumbs in the middle of the cake and place an Oreo cookie on top. Top with sprinkles if desired.
9. Return to the freezer to set up for about 15 minutes or serve immediately.

To make the Whipped Cream Frosting:

1. In a chilled bowl, beat the cream until frothy.
2. Slowly add the powdered sugar and vanilla while beating.
3. Whip until light and a thick enough consistency to spread as an icing.
4. Use immediately.