I used 1 ¾ x 1 ¾ inch ring molds to build a perfect cylinder, but you can also make them in a miniature cheesecake pan with removable bottoms. You can also make them in mini muffin tins but they will be more difficult to remove and will not be perfectly cylindrical.
Bake and cool your cookies. They should be slightly larger than the mold that you are using.
Press the ring mold over the center of the cookie like a cookie cutter; leaving the cookie inside the mold. This is your base.
Make sure your ice cream is soft but not melted. You can microwave it for 5-10 second to soften it if needed. Spoon a little of your first flavor into the mold and press it down with an offset spatula. Freeze solid.
Repeat the last step with your second flavor and freeze. If you are going to add a layer of whipped cream, leave a little space at the top.
I recommend freezing them overnight (without whipped crem) to make sure they come out of the mold easily without smearing.
When you are ready to remove the rings, gently but firmly press the cookie up through the mold like a push-pop. Place on a tray and freeze until ready to serve.