1. Make the cake Pre-heat the oven to 170℃. Using an electric mixer, beat egg whites in a bowl until soft peaks form. Gradually add sugar, and beat until firm.
2. Add the egg yolks one by one, and mix well after each addition.
3. Add the sifted flour into the egg mixture and mix gently with a rubber spatula. Do not overmix.
4. Add the oil and yogurt. Mix.
5. Spoon the batter into a lined cupcake pan and fill cupcake liners a little more than half way. (about two-third of the pan.)
6. Bake for about 13 to 15 minutes or until a toothpick inserted in the center of the cupcake comes out clean.
7. Make the topping cream In a small bowl, add all ingredients A and mix well until combined evenly. Strain the mixture to a saucepan using a strainer and cook over moderate heat. Stir constantly, until thickened, using a wooden spoon or a spatula. Let it cool and set aside.
8. Once cooled, transfer this cream mix into a bowl, beat until soft. Gradually add the softened butter and cheese cream (optional), mix until smooth. Pipe this topping cream onto the cupcakes and enjoy!