1. Sieve all purpose flour, cooking soda and powdered sugar together into a bowl.
2. Add milk, cooking oil and vanilla essence and whisk to bring together.
3. The cake batter should be lump-less and in dropping consistency.
4. Bring the cooking chocolate to room temperature and shave it using grater.
5. Preheat oven to 375 deg F or 190 deg C. Line the muffin tray with liners.
6. Fill muffin cups with cake batter up to 1/2 the height and now carefully place a spoon of chocolate shavings on top of the batter, just covering the center and not the sides.
7. Now drop in a few spoons of cake batter on top to cover the chocolate layer.
8. Bake it for 12 to 15 mins at 375 deg F or 190 deg C.
9. This quantity makes 12 soft muffins.

Tips:
Use cooking chocolate for the filling. This chocolate melts well when the cake is warm and gives a gooey center.
Spoon enough batter on top of the chocolate filling layer to avoid hole on top

Recipe courtesy: 4th sense cooking