Preheat your oven to 350°F (175°C). In a mixing bowl, combine crushed graham crackers, sugar, and melted butter until the mixture resembles wet sand. Firmly press this blend into the bottom of a 9-inch springform pan.

In a large bowl, beat together cream cheese and granulated sugar with an electric mixer on medium speed until smooth, approximately 2-3 minutes. Gradually add the heavy cream, mixing until creamy, about another 2 minutes.

Melt dark chocolate until smooth, then allow it to cool slightly before mixing into the cream cheese mixture along with orange zest and orange liqueur.

Add eggs one at a time, mixing gently on low to ensure smoothness without visible egg streaks.

Pour the filling over the crust. Create a water bath by placing the springform pan in a larger roasting pan filled with hot water. Bake for 50-60 minutes until edges are set but center jiggles slightly.

Allow to cool in the water bath for about 1 hour, then refrigerate for at least 4 hours or ideally overnight to set completely.

Carefully remove sides of the springform pan. Top with whipped cream or orange zest, serve with fresh orange slices.