To make frosting, blend all ingredients in a high speed blender until smooth, adding water as needed. Store in the fridge.
To make the cake, process the oats into flour in a food processor, then add the remaining ingredients to the food processor and process until it all begins to stick together.
Press half the cake mixture into a small spring form pan (4 inches). Gently remove and place on a plate, and freeze until solid. Repeat with remaining cake mixture. Spread 1/3 of the frosting on top of one of the cake layers. Put in freezer until frosting has hardened. Place the other cake layer on top and frost the entire thing.