'- Egg yolk batter- 1 egg- 5 egg yolks- 2 tablespoon (~ 20 gram) grated parmesan- 3 tablespoon (~ 30 gram) grated cheddar (I use sharp Cheddar)- 1/4 cup vegetable oil- 1/4 cup milk- 60 gram all purpose flour + 5 gram corn starch, whisk together- Egg white batter- 5 egg whites- 1/4 teaspoon cream of tartar- 80 gram (~ 5 tablespoon) sugar

1. Preheat oven to 320 Fahrenheit (160 Celsius), boil a kettle of water, and line an 8"x8"x2" square cake pan with parchment paper.2. Egg yolk batter: in a large mixing bowl, beat 1 egg, 5 egg yolks, parmesan, cheddar, vegetable oil, and milk until thick and slightly pale. Add in the flour mixture and whisk until just mixed.3. Egg white batter: in a large mixing bowl, whisk egg whites and cream of tartar until foamy. Add sugar in three batches, and keep on whisking until stiff, stop when it reaches medium peak.4. Fold in the egg white batter to the egg yolk batter with a spatula in 3 stages. Make sure you use folding method so you don't destroy the air bubbles.5. Pour the batter to the lined cake pan.6. Place a baking sheet (I use a half sheet pan) in the middle rack of the oven, and place your cake pan on the baking sheet. Pour hot boiling water from the kettle onto the baking sheet (not your cake pan!) so the water fills about 1/2" of the baking sheet.7. Bake for about 55 minutes to 1 hour, or just until the cake is golden brown, and a cake tester comes out clean.8. Remove the cake from the oven. Gently flip the cake onto a wire rack, and very gently peel away the parchment paper from the cake. Place another wire rack on the cake (the bottom side of your cake), and flip once more so the right side (upper part of the cake) is now facing up.9. Let the cake cool to room temperature, and cut into 9 serving pieces.