1 1/2 oz of white rum (or Light Rum)
1/4 oz of Dark rum
3/4 oz of Lime Juice
1/4-3/4 oz of sugar syrup (or simple syrup)
2-3 dash of cointreau orange liqueur (or orange liqueur)
1/2 tsp of powdered sugar (or sugar)
Shake well over ice cubes in a shaker, strain into a chilled cocktail glass, and serve.