Place the 500 g mascarpone and 300 ml whipping cream in the refrigerator for at least 2–3 hours (or keep them chilled until you are ready to whip the cream).

Preheat the oven to 180°C (356°F). Line a 36×24 cm (14×10 in) baking sheet with parchment paper (or prepare a same-size pan).

In a large mixing bowl, combine all 10 eggs and 200 g granulated sugar. Beat on low speed at first, then increase the speed and continue beating until the mixture is pale, thick and slightly increased in volume (about 5–8 minutes with an electric mixer).

Add 50 ml oil and 1 tbsp vanilla essence to the beaten eggs and sugar. Mix briefly until incorporated.

Sift together 250 g flour, 60 g cocoa and 1 sachet baking powder into a separate bowl (or directly over the egg mixture). Gently fold the dry ingredients into the egg mixture with a spatula until just combined and no flour streaks remain.

Divide the batter into two equal portions. (You can weigh the batter, eyeball, or pour half into a second prepared sheet; alternatively see step 8 for the single-bake option.)

Pour one portion of batter onto the prepared baking sheet and spread it evenly to the edges. Bake in the preheated oven for 10–12 minutes, or until the sponge is set, springs back to the touch, and a toothpick inserted near the center comes out clean or with only a few moist crumbs.

Remove the baked layer to a wire rack and let it cool completely. Repeat baking with the second portion of batter on the same prepared sheet (or bake the whole batter at once in a deeper pan and, after cooling completely, use a long serrated knife to cut the cake horizontally into two even layers).

When the sponge layers are cooling, prepare the cream. Put the chilled mascarpone (500 g), chilled whipping cream (300 ml), 150 g sugar, and 1 tbsp vanilla essence in a cold mixing bowl.

Whip the cream and mascarpone mixture on medium-high speed until it reaches stiff peaks and holds its shape. Do not overbeat—stop as soon as the cream is firm and spreadable.

Place one cooled sponge layer on your serving board or tray. Spread all of the prepared cream evenly over this layer, smoothing to the edges.

Place the second sponge layer on top of the cream. Cover the top with a plate, tray or chopping board and press gently and evenly to compact the cake (do not press so hard that cream squeezes out).

Refrigerate the assembled cake for at least 2–3 hours to set the cream before slicing. Use a sharp serrated knife to slice and serve chilled.