Preheat the oven to 350°F (175°C) and prepare two 9-inch round cake pans by greasing them with vegetable oil and lining with parchment paper.

In a clean bowl, whip egg whites until soft peaks form. Gradually add granulated sugar until stiff peaks develop, about 4-5 minutes.

Whisk together egg yolks, remaining sugar, and vegetable oil in another bowl until combined and slightly thickened, about 2-3 minutes.

Sift all-purpose flour into the egg yolk mixture and fold gently to create a smooth batter.

Fold the whipped egg whites into the batter in three additions, being careful not to deflate the mixture.

Pour the batter into the prepared cake pans and bake for 25-30 minutes.

Cool the cakes in the pans for 10 minutes, then transfer to wire racks to cool completely.

Prepare mango syrup by combining chopped mango with water in a saucepan and heating until broken down into syrup, about 10 minutes.

Whip heavy cream with vanilla extract until stiff peaks form, about 3-5 minutes.

Layer the cake starting with one layer on a serving plate, brushing with mango syrup, followed by whipped cream and mango pulp. Repeat with the second layer.

Frost the top and sides of the assembled cake with remaining whipped cream and decorate with fresh sliced mangoes.