Rob Roy 1 1/2 ounces Scotch Whiskey 1/2 ounce sweet vermouth 1 dash orange bitters Stir with ice. Strain into a cocktail glass. Garnish with lemon twist. Also known as: Santiago Scotch Plaid Bitters: Orange bitters was an original ingredient for this drink, but with this often being difficult to find Angostura bitters can be used instead.