Mix all cake ingredients (excluding the orange liqueur) in a bowl and beat with an electric mixer for 2 minutes.

Divide the batter between 2 greased and floured 10-inch cake pans.

Bake at 325°F for 25-30 minutes, until a toothpick inserted into the center comes out clean.

Cool completely on wire racks.

Once cool, poke the surface of each cake layer with a fork and drizzle 1 ounce of orange liqueur over each.

In another bowl, cream together the cream cheese and 1 cup of sugar.

Add the eggs one at a time, beating well after each addition.

Mix in the vanilla extract, orange zest, and 3/4 cup heavy cream.

Pour the mixture into a 10-inch springform pan lined with parchment paper.

Bake at 325°F for 50-60 minutes, until the surface is no longer glossy.

Run a knife around the edge to release the cheesecake and cool completely in the pan.

Once cool, place one chocolate cake layer on top of the cheesecake in the springform pan.

Invert onto a serving plate, release the springform pan, and remove the pan and parchment paper.

Top with the second cake layer.

Mix together powdered sugar and 1/2 cup cocoa.

Blend in softened butter until smooth.

Add milk as needed to achieve a spreadable consistency.

Spread a thin layer of frosting over the cake's sides and top.

Refrigerate for 1-2 hours.

Melt chocolate chips and 1/2 cup heavy cream together in a double boiler, stirring constantly.

Cool the ganache to lukewarm, then pour over the center of the cake.

Spread quickly with a spatula, allowing it to flow over the sides.

Garnish with orange slices.