• Note: I recommend checking the steps with images and/or watching the video. The recipe might seem long, but that's simply because I’m explaining the steps for two different types of loaf pans.
• You can use a food processor (blender)or a stand mixer with a paddle attachment, like a KitchenAid, to prepare the batter.
• Cream the butter, sugar, and salt.
• Incorporate the sifted flour (300 g / 10.6 oz) with the baking powder and mix well.
• Add the eggs one at a time, mixing well after each addition.
• Gradually add the heavy cream once the eggs are fully incorporated into the batter. Mix well to obtain a smooth batter.
• Divide the batter into two equal parts (about 608 g / 21.5 oz each). To do this, weigh the empty bowl you'll use beforehand.
• You should end up with two portions of approximately 608 g (21.5 oz) each.
• Add the cocoa powder (30 g / 1 oz) to one portion and the 15 g (0.5 oz) of flour and vanilla to the other. Mix well.
• Divide the marble cake batter into two equal parts.
• Place each batter in a piping bag without a nozzle or a freezer bag.
• Grease and line the bottom and sides of a regular loaf pan, or grease the tube pan along with the tube and inside the lid. Line the bottom with parchment paper.
• Alternate between the vanilla and chocolate batters, starting by piping the vanilla batter in the shape of a W. Then pipe the chocolate batter in the same W shape on top. Watch the video for a clearer explanation.
• Tap the mold gently against the work surface to smooth the top.
• Place a small amount of softened butter into a small piping bag or a freezer bag. Pipe a thin line of butter down the center of the batter, along the entire length of the mold.
• Refrigerate the mold overnight, or place it in the freezer for 1 hour if you're in a hurry.
• After the chilling time, preheat the oven to 150°C (300°F) preferably with fan.
• Bake for 1 hour and 30 minutes. A skewer inserted into the center of the cake should come out dry.
• If you chose a loaf tube pan, proceed in the same way. Alternately pipe the two batters until you reach the hole, then insert the tube.
• Continue piping, alternating between the vanilla and chocolate batters.
• Tap the pan on the work surface to smooth the top, and close with the lid.
• Bake immediately for 1 hour and 30 minutes at 150°C (300°F) (fan-assisted oven preferred).

Soaking syrup:

• Prepare it a little before the end of the cake's baking time, as it should be lukewarm.
• Combine the water and sugar, and bring to a boil over medium heat. Stir to dissolve the sugar. Do not let it boil to avoid evaporating the water.
• Remove from heat and add the vanilla extract or rum.

The finishing :

• Unmold the marble cake onto a wire rack.
• For the cake with a tube, wait about ten minutes, then gently remove the tube by twisting it in one direction, then the other.
• Soak the warm cake with the lukewarm syrup on all sides (except the bottom).
• Wait for it to lose some steam, then wrap it completely in plastic wrap.
• Leave it until the next day or from morning to evening (minimum 4 hours) at room temperature.

Prepare the ganache

• The next day, prepare the dark chocolate ganache if you made a marble cake in the tube loaf pan. Otherwise, proceed directly to the chocolate Rocher glaze step.
• Melt the dark chocolate over a double boiler.
• Once the chocolate is melted, heat the heavy cream with the inverted sugar or honey.
• Add the hot cream to the melted chocolate in 3 or 4 stages. Stir with a spatula in a circular motion. The ganache may seem to separate, but don't worry, this is normal.
• Continue adding the rest of the cream until you have a smooth, glossy ganache.
• You can use an immersion blender, trying not to create air bubbles.
• Place the ganache in a piping bag.
• Remove the plastic wrap from the cake, then wrap one side of the cake tightly. If necessary, double the plastic wrap to seal the gap and prevent the chocolate ganache from spilling out.
• Place the cake vertically (standing upright) in a container that can hold it steady. 
• Fill the hole with the ganache, which should be liquid but not too runny. Fill it to the top.
• Refrigerate for about 15 minutes and add more ganache if necessary, as it may settle slightly.
• Freeze the cake with the ganache in this position for 1 to 2 hours to make it easier to glaze. 
• If you opted for a cake without ganache, freeze it as well for 1 to 2 hours. 
• The thermal shock will allow the glaze to adhere to the cake, and this way, you can use the hot glaze. It will flow smoothly without forming any clumps of glaze on the cake.

Rocher Glaze

• Roast the Roast the finely diced blanched almonds for about 15 minutes in a preheated oven at 160°C (320°F) and let them cool.
• Melt the chocolate in a double boiler. When melted, add the oil and mix well.
• Remove from heat, add the toasted almonds and mix well.
• Place a wire rack on a tray lined with two sheets of aluminum foil. These two sheets will catch the glaze and allow you to pour it back over the cake.
• This step should be done quickly before the glaze sets on the cake.
• Remove the cake from the freezer and put it on the wire rack.
• Pour the glaze over the entire surface to cover it completely. Pour back any excess that has spilled onto the sheets. With this method, you'll have a generous layer of glaze.
• Tap the rack to spread the glaze evenly. I recommend not using a spatula. I did it on one side, and it left marks.
• Slide two large spatulas under the cake and transfer it to the serving platter. Do this once the rocher glaze has stopped flowing.
• Let it sit at room temperature before enjoying.