Take wheat flour, cocoa powder, baking powder and baking soda in sieve
Sieve them for 6-7 times and keep it ready.
Take milk in a bowl and add vinegar.
Mix it nicely and keep it aside for 5 minutes.
In the frothy milk add sugar, oil and vanilla essence and mix it nicely till sugar is dissolved.
Add flour in batches and mix
Mix nicely without lumps till everything is combined
Pour the batter in greased tin
Preheat the oven to 180°C for ten minutes and bake in the same temperature for 45-50 minutes till toothpick inserted comes out clean.
Cool them in wire rack.
Similarly prepare two more sponge cakes using the same measurements. Since my oven is small, I baked two sponge in oven and one in cooker to save the time.