To begin making the Chocolate Orange Marble Cake recipe, we will first begin by preheating the oven to 180 C.

Place the chocolate in a sauce pan. Melt the dark chocolate using a double boiler method. In this method, you place a bowl of water in a pan on medium high heat. Place this sauce pan which has chocolate, over this pan of boiling water. 

Keep stirring until the chocolate melts completely and becomes smooth.

Next, line a cupcake pan or a spring foam pan or a loaf pan with butter paper or parchment paper and set aside. You can also grease the pans with butter and dust with flour. 

In a large mixing bowl or the bowl of the stand mixer; whisk the butter and sugar until light and fluffy. Gradually add in one egg at a time and beat until fluffy. Add in the orange juice, the zest and the flour a little at a time until well combined. 

Pour in half the cake batter into the prepared tin. Drizzle the melted chocolate into the marble cake batter and pour the remaining cake batter over this. With the help of skewer, create a marbling effect on the batter, by swirling it around. Drizzle the remaining chocolate sauce over the batter and create a marble effect for this cake batter too. 

Place the cake pan into the preheated oven and bake for 30 to 45 minutes until the tester when inserted into the cake comes out clean. 

Once the chocolate orange marble cake is baked, remove from the oven and allow it to cool for at least 5 minutes before you an invert, cut and serve. 

Serve the delicious Orange Chocolate Cake along with breakfast or as a tea time snack with a cup of coffee.