Although base for an ice cream sandwich is traditionally a cookie or wafer, a brownie can be ideal for creating a compact, cocoa-heavy treat. The texture of the brownie is extremely important; too soft and fudgy and it will "bleed" over the cream; too hard and it will fail to contain the sandwich contents. A soft, slightly cake-y brownie is just about perfect.
I suggest using an over-sized rectangular pan when baking, so the batter spreads out to form brownies that are just a bit thinner than average. Then, cut out circles of cooled brownie or use your favorite cookie cutters for more creative shapes. For the sake of uniform circumferences, you may want to use an upside-down water glass.
Next, top your bottom base with a scoop of ice cream. Top with matching brownie base and smoosh slightly to meld the layers. Enjoy promptly or wrap in plastic wrap for consumption at a later point.
Now, obviously, you can apply any type of ice cream you like to this recipe, but why not continue with the chocolate theme and select an inventive cocoa-based flavor? This time I used plain Dutch Chocolate, but next time let's introduce some legumes via this bad boy.