If you're using the egg white (which I STRONGLY recommend), put that in the shaker first and give it a really strong "dry" shake by itself for 15-20 seconds.
Then add the banana-infused bourbon, lemon juice, cinnamon simple syrup, and bitters (if using) to the egg white in the shaker, and shake for another 15 seconds.
THEN, add ice to the shaker and give the mixture another shake for 10-15 seconds (to cool it down, mostly, plus a little more emulsifying and getting a really good foam).
Taste to make sure it's balanced to your personal taste. You can always add a little more of anything to get it there.
Strain into a coupe glass and garnish as desired...dehydrated citrus slice is nice, a caramelized banana slice would be good, or a few pretty drops of darker bitters.