The Old Fashioned is one of America's earliest cocktails. It has very few ingredients, but is very complex and is quite challenging. Brown sugar syrup adds extra flavor and works very well with the bourbon. If you use a different base, such as Crown Royal Canadian whiskey, brown sugar syrup might be too overpowering. Bitters is an important part of the Old Fashioned and the amount is entirely up to you (although omitting the bitters is not an option). Adding the orange zest is highly recommended and you can also use other citrus such as a tangerine, grapefruit, lemon, lime, or maybe even a kaffir lime. You can also use other types of bitters, such as orange bitters or peach bitters which might be interesting. There are many possibilities, so experiment to find a combination that works for you. Mix an Old Fashioned like a pro at your next cocktail party.