Preheat the Oven: Preheat your oven to 180°C (350°F). Grease the 30 cm plum cake mold with a bit of sunflower oil or line it with parchment paper for easy removal later.

Beat the Eggs: In a large mixing bowl, crack 3 medium eggs and add a pinch of salt. Beat them with a whisk or an electric mixer until they become slightly frothy.

Add Sugars: Gradually add 160g of sugar and 8g of vanilla sugar (or 1 sachet of vanillin) to the eggs, continuing to whisk until the mixture becomes pale and fluffy. This process usually takes about 3-5 minutes with an electric mixer on medium speed.

Incorporate the Liquids: Slowly pour in 120 ml of sunflower oil while whisking, followed by 180 ml of milk. Continue whisking until the ingredients are fully combined and the mixture is smooth.

Add the Dry Ingredients: Sift 250g of all-purpose flour and 15g of baking powder together into the wet mixture. Fold the dry ingredients gently into the wet mixture using a spatula or whisk, being careful not to overmix. You want the batter to remain light and airy.

Separate the Batter: Once the batter is fully combined, divide it into two equal parts by pouring half of the mixture into another bowl.

Make the Chocolate Batter: In one of the bowls, sift 20g of bitter cocoa and add 3 tablespoons of milk. Stir gently until the cocoa is fully incorporated into the batter, creating a smooth chocolate mixture.

Layer the Batters: Start by pouring a portion of the vanilla batter into the prepared plum cake mold, spreading it evenly. Then, pour a layer of the chocolate batter on top of the vanilla layer. Continue alternating between the vanilla and chocolate batters until both batters are used up.

Create the Marble Effect: To create the signature marble pattern, use a knife or skewer to swirl the batters together. Insert the skewer into the batter and make circular motions, moving from one end of the cake mold to the other. Be careful not to overmix; you want distinct swirls of chocolate and vanilla.

Bake the Cake: Place the cake in the preheated oven and bake for 45-50 minutes, or until a toothpick inserted into the center of the cake comes out clean. Keep an eye on the cake toward the end of the baking time to ensure it doesn’t overbake.

Cool the Cake: Once baked, remove the cake from the oven and let it cool in the mold for about 10 minutes. Then, gently transfer it to a cooling rack to cool completely before slicing.

Slice and Serve: Once cooled, slice the cake and serve. This cake pairs wonderfully with coffee, tea, or even a dollop of whipped cream. The beautiful marbled pattern inside makes each slice visually appealing, and the taste is sure to delight everyone.