Fluffy Cake with Whipped Mascarpone-Caramel Filling

• Vegetable oil: 50g (about 3 and 1/2 tablespoons)
• Milk: 50g (about 3 and 1/2 tablespoons)
• Cake flour: 55g (about 1/2 cup minus 1 tablespoon)
• Eggs: 5 large (about 280g total, each approximately 56g)
• Granulated sugar: 50g (about 1/4 cup)
• Vanilla extract: 5g (about 1 teaspoon)

For the Filling:

• Heavy cream: 500ml (about 2 cups)
• Mascarpone: 150g (about 2/3 cup)
• Caramel: 150g (about 2/3 cup)

1. Preheat the oven to 155°C (310°F). Separate the eggs, placing the egg whites in the fridge to keep them cool.
2. In a clean bowl, thoroughly mix vegetable oil and milk. Add cake flour and mix until smooth. Incorporate egg yolks and mix until smooth. Set aside.
3. Remove the egg whites from the fridge. Add lemon juice (not listed in the ingredients but mentioned in the procedure—use about 1 teaspoon), granulated sugar, and vanilla extract to the egg whites. Beat with a hand mixer until soft peaks form.
4. Fold a small amount of the beaten egg whites into the yolk mixture gently until just combined. Then, fold in the remaining beaten egg whites gently until the batter is smooth.
5. Line a cake pan with parchment paper or a baking mat. Pour the batter into the pan, smoothing the surface. Tap the pan a few times to remove any air bubbles. Bake for 30 minutes.
6. Remove the cake from the oven and let it cool on a wire rack before removing it from the pan. Once cool, gently loosen the edges with a spatula, invert the pan onto a piece of parchment paper, remove the pan, and gently peel off the parchment paper.