It sounds pretty simple, whiskey, sugar, water (a mere splash) bitters and an orange twist. The devil is however in the details (Some thing the fountain room at the Bellagio would do well to remember). Here is how it ought to be done.
Put a teaspoon of sugar in an Old fashioned glass and add bitters (2-5 dashes), add a drop of water, stir, slowly add whiskey & ice stirring till the sugar is dissolved, it'll take a good 5-10 minutes, add an orange twist. (M.A.S.H. ever the arbiter of cocktail taste give this advice from hotlips "An old fashioned, not a fruit salad). Some how ever insist on a cherry.
When done right it's a great drink, let us not get into what happens when it's done wrong.
In a molecular mixology style there is a great recipe involving bacon infused bourbon, maple syrup & bitters. Here is the finished article
It tastes wonderful, if you've ever had maple cure bacon or maple syrup bacon pancakes you'll recognize it imeadiately, but it is really subtle. Next time though a touch more bitters & a touch less syrup.