Pre-heat oven to 325° F.
Lightly grease the bottom, but not the sides, of a 9 or 10-inch springform pan.
Line the bottom with a sheet of parchment paper for easy release from the pan later, once the cheesecake has cooled.
In a medium bowl, mix together the cookie crumbs, melted butter and 3 tbsp. sugar and press into pan.
In a separate bowl, cream together the cream cheese and 1 ¼ cups sugar.
Add the eggs, one at a time, mixing well after each addition.
Add the vanilla extract and whipping cream; blend until smooth.
Divide mixture into 2 equal portions, in separate bowls.
To the first half of the mixture, stir in the melted chocolate.
Pour into bottom of the prepared springform pan.
To the second half of the mixture, stir in the finely grated and chopped zest of 1 large orange.
Carefully spoon this mixture over the top of the chocolate mixture already in the pan.
Bake for about 60 minutes or until the surface of the cake no longer looks glossy.
Remove from oven and immediately run a sharp knife around the edge of the pan to release the cake.
Cool completely in the pan.
Top with the ganache glaze.
