In a food processor, add the frozen blueberries, almond milk, and stevia extract. Puree until almost completely smooth.
In a small bowl, whisk together the protein powder and xanthan gum. Dump this into the processor and blend again. After about 10 seconds, scrape down the sides of the processor to catch any powder that flung up, then blend again.
Blend for ~1 full minute, or until the mixture doubles in volume and turns a nice blue/purple color. Serve immediately.