Combine everything in a blender and blend for 90 seconds until thick and smooth. Add a little water or milk if the consistency is too thick.
Serve immediately.
Notes
To freeze bananas, simply peel ripe bananas, wrap them individually in plastic wrap, then keep them in the freezer until needed.
For the collagen peptides, I use Vital Proteins. Collagen peptides are unflavored and unsweetened, so they don't affect the taste of the smoothie. You can also use any protein powder of your choice, but these are usually flavored and artificially sweetened.
For the peanut butter, I love Adams natural peanut butter.
For the cocoa powder, I love Cacao Barry Extra Brute Dutch processed cocoa powder.
To make this without the egg whites, you can use any milk of your choice instead.