Preheat the oven to 325F. Double wrap the bottom of a 9-inch spring form pan with aluminum foil. Prepare a large baking sheet for the water bath; the spring form pan needs to fit comfortably.

Prepare the chocolate crust first. Place the crackers into a food processor and pulse for a few minutes, until the cookies are broken down into crumbs. Add the melted butter and pulse again until the crumbs are well coated. Press the crumbs into the bottom of the spring form pan, creating a firm crust.

For the chocolate batter: place the softened cream cheese and ricotta cheese into a large mixing bowl. Mix on medium-high speed, scraping down the sides of the bowl often, for 5 to 6 minutes, until the mixture is creamy. Next, add the melted chocolate, cocoa, vanilla, and sugar. Combine the instant coffee and boiling water in a small ramekin, then add to the batter. Beat on medium speed for a few minutes, until the mixture is uniform.

Add the eggs, one at a time, and mix for a few seconds after each addition. Add the orange marmalade, orange oil and orange zest. Mix for about a minute, just until all ingredients are well combined.

Pour the chocolate cheesecake batter over the crust and level off the top with a spatula. Place the spring form pan into baking sheet and add enough water to the baking sheet to cover the bottom and go up the sides, about 1/2-inch.

Bake in preheated oven for 1 hour 45 minutes to 2 hours, until the edges are well set and the center is just slightly wobbly. Once the cheesecake is done baking, open the oven door a few inches and allow the cake to cool for an hour. Cool completely at room temperature, then refrigerate overnight.

When ready to serve, transfer the cake onto a cake stand (check out my video to see how it's done!). Prepare the orange whipped cream. Place the chilled heavy cream, confectioner's sugar and vanilla in a large mixing bowl. Whisk on high speed for 3 to 4 minutes, until stiff peaks form. Add the orange zest and whisk again for a few seconds until it's well mixed.

Pipe the whipped cream onto cheesecake; I used Ateco tip #847. Garnish the top with sliced oranges. If not serving right away, keep the oranges off the cake until ready to serve.