Add yogurt and baking soda to the pan and mix using a spatula till its bubbly and voluminous.
Add sugar, oil and milk to the same mixture and mix again to form a homogenous mixture.
Add the flour, cocoa powder and baking powder to the above mixture and fold in till no lumps of flour remain.
Place a tawa on low-medium heat and once its hot, place the pan with cake batter over it. Cover the pan and cook for 30-35 mins. Insert a skewer to check if done.
Once done, remove the pan from heat and place mixed chocolate callets on top of it.
Cover with lid for 5 mins and let the chocolate melt on top.
Recipe by Bake with Shivesh at https://bakewithshivesh.com/chocolate-wholewheat-cake-in-a-pan/