First to the milk add vinegar and mix it well, keep it aside.

Now mix all dry ingredients in a bowl and sieve it two times.

Now add butter and sugar in a bowl and whisk it well, now add milk and vanilla essence, now fold dry ingredients to the wet ingredients.

Add some grated chocolate and mix. Now in a liners fill batter and bake it in preheated oven at 170 degree to 12-15 minutes.

Note: I used mini liners so baking time is less.