Take ¾ cup butter out of the fridge and let it soften for some time. The key is to get the butter to right temperature. We do not want the butter to melt or be rock hard.
Once butter is soft enough for mixing add 1 cup powdered sugar to it and mix well till it forms a smooth paste.
In another bowl mix the remaining dry ingredients i.e. 1 ½ cup flour (maida), 1 cup milk powder, 2 tbsp cocoa powder, 1 ½ tsp baking powder and ½ tsp cooking soda. Mix well and keep aside.
Add milk and dry mixture (made in step 3) slowly to the butter-sugar paste and keep whisking. Add 1 tsp (or 40 drops) vanilla essence and juice of ½ lemon and mix well. We are now ready to bake.
Pre-heat the oven to 100 degree celsius for 5 minutes. Cover a baking dish with butter paper or brush it with butter and pour the batter into it. Place the baking in the oven and increase the temperature to 180 degree celcius. Your very own chocolate cake will be ready in 40 mins.