Coat chilled old fashioned glass with Absinthe or its substitute (Herbsaint, Pernod, ...). Pour out most of what remains, perhaps leaving a small puddle in the bottom of the glass. Add bitters and syrup. You can use a single sugar cube instead of simple syrup, in which case you would now muddle this to dissolve. Add Whiskey. Garnish with a twist of lemon peel.