In a rocks glass, muddle together the sugar cube, angostura bitters and splash of club soda until sugar is dissolved.
Add desired ice (see note) and fill with whiskey.
Garnish with orange peel.
notes
You can make this cocktail with regular ice, a large ice sphere, or no ice at all, if desired. If you are making it without ice, be sure to thoroughly chill the rocks glass and Jameson whiskey before serving.