Place two bowls in the freezer to chill (optional, but it will keep the smoothie from melting too fast).Put all of the base ingredients in a high-powered blender. You will need a blender with a wand, so you can press the mixture down into the blade (if you don't have this, it will be difficult to make a thick smoothie bowl).Blend using the "ice" or "frozen" setting. While blending, constantly push down the mixture into the spinning blade using a wand and guard (to keep you from pushing the wand too far down and into the blade). This will likely be a noisy process, but keep pushing the mixture down. I usually run it through two cycles to ensure that everything is blended well.Once the smoothie mixture is well blended, scoop it out and into the chilled bowls, add any desired toppings, and enjoy immediately.