Preheat oven to 350°F. Lightly grease a 9-inch springform pan and line the bottom with parchment paper.
In a medium bowl, combine the graham cracker crumbs, sugar, rosemary and olive oil. Press the mixture onto the bottom of the prepared pan in an even layer.
In a large bowl, beat the cream cheese with an electric mixer until smooth and creamy. Add the sugar and flour and beat until well combined.
Add the eggs, one at a time, beating well after each addition. Stir in the whiskey and melted chocolate.
Pour the filling over the crust, spreading it evenly with a spatula.
Bake the cheesecake for 50-60 minutes or until the edges are slightly golden and the center is set.
Meanwhile, prepare the topping. In a small saucepan, combine the blood orange juice, grapefruit juice, cornstarch and sugar. Whisk until no lumps remain.
Heat over medium-high heat, stirring constantly, until the mixture thickens and comes to a boil. Reduce the heat to low and let simmer for 2-3 minutes.
Remove from heat and let cool to room temperature.
Once the cheesecake has cooled to room temperature, cover it with plastic wrap and refrigerate for at least 2 hours or overnight.
Before serving, pour the blood orange and grapefruit topping over the cheesecake, spreading it evenly with a spatula.