First, pour two parts Hennessy into a cocktail shaker filled with ice, followed by two parts blood orange vodka, and 1.5 parts fresh lemon juice. Add 1 part agave nectar, and a dash of bitters.
Cover and shake the cocktail shaker until frosted, and then strain into a highball or Old-Fashioned glass. Arrange the blood orange twist in the middle of the drink. Enjoy!
Notes
You can find blood orange vodka online, or at local retailers. The easiest one for me to find was Skyy Blood Orange Vodka, which I bought at Safeway.