Place the sugar cube (or sugar) in the bottom of a rocks glass. Add bitters and a few drops of water.
Tip: If using granulated sugar, stir until it mostly dissolves before adding ice.
Muddle gently until the sugar begins to break down and dissolve, forming a syrupy base.
Add the bourbon and stir to combine.
Place a large ice cube (or a few smaller ones) into the glass. Stir again for 15–20 seconds to chill and dilute slightly.
Tip: A large cube melts slower, keeping your drink cold without watering it down too quickly.
Express the oils from an orange peel over the glass by holding it over the drink and giving it a twist. Rub the peel around the rim, then drop it in.
Add a Luxardo cherry if you like a touch of sweetness, though purists may prefer to skip it.
Sip slowly and enjoy.