Add all ingredients in a cocktail mixing glass and shake cocktail with ice. Strain over fresh ice in cocktail glass. Add a splash of sparkling water and garnish with an herb leaf - sage, rosemary or basil.
In a mixing glass, add bitters and sugar cube and muddle thoroughly. Add whiskey and ice, stir until chilled. Prepare cocktail glass with a rinse of absinthe or herbsaint and empty. Strain over fresh ice into the cocktail glass. Garnish with lemon peel twist.