In order for a whiskey sour to be truly great, you've got to squeeze your lemons fresh. You'll end up with a cocktail that, unlike most whiskey drinks, is actually refreshing. This is something you'd want to sip on while sitting on the front porch.
Separate egg and whisk egg whites just enough to break down for easy measuring. Set aside. In a mixing glass, combine lemon juice, simple syrup, bourbon, egg whites, and bitters. Dry shake (without ice) to emulsify ingredients. Add ice cubes, seal, and shake again. Strain whiskey sour into a chilled glass with ice. To garnish, spear one end of the orange slice with a cocktail pick, then the cherry, then the other end of the orange slice; place atop the drink and serve.