Cut parchment paper into four 7” (18 cm) rounds.
Separate eggs into yolks and whites in different bowls.
Whisk flour and baking powder together.
In a bowl with the yolks, add half of the sugar, the flour mixture, oil and water. Whisk very well until the sugar has dissolved completely. Set aside.
In a bowl with the egg whites, add the other half of the sugar slowly while whipping with an electric hand mixer. Whip until stiff peaks form. Take some of this meringue, add to the yolk mixture and mix. Then fold the meringue in 2 parts in the yolk mixture. Take care not to deflate the foam in the batter.
Heat a frying pan at low heat. Place a round of the parchment paper in the pan, and pour half of the batter on it. Cover and cook 4-5 minutes. Place another paper round on top of the batter, turn over, cover, and cook another 4-5 minutes. Repeat for another cake.
Cool cakes a few minutes and remove the paper. Fold the cake gently in half without breaking. Wrap with plastic to hold the shape.
Cut off the ends of the bananas and peel. Whip heavy cream with sugar to form medium to stiff peaks.
Pipe a line of whipped cream in the middle of the cake, place a banana along it. Fold the cake and pipe more cream next to the banana. Sprinkle powdered sugar on top if you like. Repeat for a second cake.
