Shake all the ingredients with ice and strain into a chilled cocktail glass. Garnish with the flamed orange peel.
One of my favorite cocktail authors, David A. Embury, refers to this cocktail as the spawn of the Prohibition toad. But he does reluctantly offer his recipe: 2 parts gin to 1 part orange to .5 part Simple Syrup. Modern tastes lean toward a lighter drink, so I altered the recipe and added Cointreau instead of Simple Syrup to bring a bit of flavor along with sweetness.