- In a mixer bowl, combine the egg whites together with a pinch of salt, then beat until you get a thick beer-like foam. Gradually add the ⅔ of sugar, sprinkling it on top of the mixture, then whip it to soft peaks.
- In a separate bowl, combine the egg yolks with the rest of the sugar, then beat until it increases in volume considerably.
- Pour the warm kefir into a glass, then add 0,5 tsp of baking soda and mix until the kefir mixture reaches its maximum volume.
- After that, add the vegetable oil and mix it all together, then pour the mixture into the whipped egg yolks.
- Whip one more time, then combine with the meringue mixture.
- Sieve the flour, starch and baking powder into the mixture in the bowl in several passes.
- Pour the mixture into a baking pan and bake at 170C (338F) for about 35-40 minutes.
The key ingredient to make a good sponge cake is egg whites thoroughly whipped with sugar + egg yolks whipped with sugar+kefir mixed with oil as well as flour that is carefully folded in last of all.
It’s also IMPORTANT TO REMEMBER TO WRAP YOUR SPONGE IN PLASTIC WRAP AND LEAVE IT IN THE FRIDGE FOR 6 HOURS BEFORE ASSEMBLING THE CAKE.