Sponge cake with caramel filling

Preheat the oven to 170°C (top-bottom; for convection 160°C). Prepare a springform pan with a diameter of 18–20 cm: line the bottom with a circle of baking paper, grease the sides with a thin layer of butter, and optionally dust with flour (pressing out the excess). Take the eggs out of the fridge about 30 minutes in advance to reach room temperature — this will make whipping easier.

In a large, dry, degreased bowl, crack all the eggs and add 120 g of sugar for the sponge cake along with a pinch of salt. If you are using vanilla extract, add it now. Start mixing with a spiral whisk first on low speed for 20–30 seconds, then increase the speed to medium-high and beat for 8–10 minutes until the mixture becomes pale, very fluffy, and at least doubles in volume — the mixture should form a 'ribbon' that falls from the whisk (meaning it leaves a clear trace for a few seconds when lifted).

Sift the all-purpose flour through a sieve directly over the egg mixture, dividing it into three portions. Using a wide rubber spatula or wooden spoon, gently combine the flour with the mixture using the 'folding' technique: insert the spatula into the center of the bowl, roll the dough from the bottom over the top, turning the bowl 90°, and repeat quickly and gently. Avoid mixing in circular motions to prevent deflating the mixture. Work briefly — combining all portions of flour should take 2–3 minutes. The mixture is ready when there are no visible white streaks of flour and it has a uniform, light consistency.

Gently pour the batter into the prepared pan, spread it evenly with a spatula, and lightly tap the bottom of the pan on the counter to remove larger air bubbles. Place in the preheated oven and bake for 25–30 minutes at 170°C (if using a convection oven, set to 160°C). The cake is ready when the top is golden, springy to the touch, and a skewer inserted comes out dry or with a few moist crumbs, but no raw batter.

After baking, remove the pan from the oven and let it sit for 10 minutes, then gently separate the sides with a knife and remove the springform ring. Turn the sponge cake upside down onto a cooling rack and leave it to cool completely (about 30–40 minutes). Before cutting, make sure the sponge cake is completely cold — if warm, it will crumble.

In a medium, wide saucepan/grill pan with a thick bottom, evenly sprinkle 150 g of sugar for caramel. Set over medium heat and allow the sugar to dissolve: do not stir with a spoon, but gently shake the pan every few seconds to ensure it melts evenly. At first, the sugar will become clumpy, then it will start to clarify — when most of it is liquid and reaches a golden-amber color (about 5–8 minutes), immediately move on to the next step. Be careful, as caramel can quickly go from golden to bitter.

Remove the saucepan from the heat and carefully add the cold butter, piece by piece (40 g), vigorously stirring with a wooden spoon or silicone spatula until the fat melts and forms an emulsified, smooth mixture. Once the butter is combined, gently heat the cream (200 ml) — it should be just warm, not hot — and pour it in a thin stream into the caramel, stirring constantly. Note: the mixture will steam heavily and may bubble. After adding all the cream, place the saucepan over low heat and cook for 2–3 minutes, stirring, until the mixture thickens slightly. Finally, add a pinch of salt and mix well.

Let the caramel cool for about 10–15 minutes until it is warm but thicker (it should flow from the spoon in a thick ribbon). If the caramel has become too hard, briefly heat it over steam or on low heat, stirring.

Once the sponge cake has completely cooled, carefully cut it horizontally into two equal layers using a long serrated knife. Hold the knife horizontally and make gentle sawing motions to avoid tearing the structure. If the sponge cake cracks, chill it in the refrigerator for another 10–15 minutes before cutting.

Spread about half of the warm caramel (approx. 120–140 g, depending on thickness) over the bottom layer of the sponge cake, smoothing it evenly with a wide spatula. Place the top layer on and drizzle the remaining caramel over the top. You can reserve a few teaspoons of caramel for decorative "drops" when serving.

Optionally, sprinkle the cake with sifted powdered sugar just before serving for visual contrast. Cut into 4 equal portions with a sharp knife (preferably warm — rinse it with hot water and dry it before cutting), serve on plates with a teaspoon of cream or a portion of seasonal fruits (e.g., thin slices of apple or pear).

Place the assembled cake in the refrigerator for at least 1 hour so that the caramel thickens slightly and the layers 'bind' together. Take it out 10–15 minutes before serving so that the caramel is not too hard and the flavor is more pronounced.