Recipe from Jeffrey Morgenthaler

1½ oz Amaretto (I used Luxardo, but Disaronno works as well)
¾ oz cask-proof Bourbon (I used Penelope Barrel Strength Four Grain - 115 proof)
1 oz lemon juice
1 tsp 2:1 simple syrup
½ oz egg white

Combine ingredients in shaker
Blend with immersion blender until egg whites frothy
Add ice and shake
Double strain over fresh ice

This taste like a whiskey sour variation and it is delicious. Using the immersion blender gives you great foam with minimal effort.