Preheat oven at 180°C.
Wash, peel, cut mangoes into cubes and blend until fine puree. Pour the puree through a sieve. Use fresh and pulpy mangoes. I used Alphonso mangoes.
Mix all wet ingredients Oil, Vanilla essence, mango puree, milk in a bowl. Add sugar. Whisk well till sugar dissolves and mixtures becomes fluffy.
Add vinegar. Whisk again.
Sift maida, baking powder, baking soda together twice or thrice for any impurities. Add salt. Mix well. Keep aside.
Mix dry ingredients slowly into mango mixture. Fold gently. (Add milk if required to adjust the consistency)
Divide this mixture into two parts.
Take sifted cocoa powder and coffee into a bowl. Add slightly warm water slowly and Mix well into a smooth paste.
Add cocoa-coffee mixture into ½ part mango flour mixture. Mix well till it incorporates well with each other.
Grease baking pan with oil. Dust it with flour and spread evenly.
Pour the ¼ mango flour batter in a greased pan. Drop ¼ cocoa coffee batter on mango flour batter randomly. Using fork or knife draw lines into the batter to get a marble effect.
Pour remaining mango flour batter on top. Spread evenly. Drop ¼ cocoa coffee batter randomly and repeat the process.
Lightly tap the pan so that batter is spread evenly and there are no air bubbles.
Bake for 35-40 minutes. Insert a toothpick, it should come out clean. Let the pan sit on the counter for 5 minutes.
Flip cake and let it cool on wire rack.
Serve with hot tea.
