In a bowl, add 4 egg whites, 1/4 tsp cream of tartar and whip it until foamy.
Add in 1/4 cup of sugar and continue whipping until stiff peaks
In another bowl, sift 1 cup of cake flour, '6 cup sugar, 1 tbsp cocoa powder, and 1 tsp salt
Also sift in 1 tsp of baking powder. Mix well, and set aside.
In another bowl, add 4 egg yolks, 1 /4 and 2 tbsp vegetable oil, 1 /3 cup evaporated milk, and 2 tbsp of coffee granules with 2 tbsp of water and whisk everything together.
Add half of the dry mixture and add the remaining of the dry mix-ture and mix well.
Fold in the egg whites in two batches, by scraping down the side and in the middle
Pour in half of the batter into an 8x8 inch baking pan lined with parchment paper and tap 3 times to remove air bubbles. Similarly, do the same steps for the remaining of the cake batter.
Bake at 160 degree celsius for 13 to 15 minutes. Check by poking the toothpick at the center of the cake
If the toothpick comes out clean, your cake is done!
Flip your cake and place it on the baking rack to cool. Once cooled, remove the parchment paper and set aside. Similarly, do the same for the second batch of the batter.
To make the frosting, in a small bowl of 2 tbsp of coffee granules, add 1 tbsp of cocoa powder and 1/4 cup of evaporated milk. Mix well and set it aside.
In another bowl, cream 1 cup of unsalted butter until light and fluffy
Add the coffee mixture earlier and mix well and scrape the sides
Add half of the powdered sugar and mix, and add in another half and mix thoroughly.
Assemble the cake and add the frosting. Cover the whole cake with frosting. For leftover frosting, using a star shaped tip, pipe around the edges