Take pan add cocoa powder,sugar,chocolate bars,cornflour half of the milk(1/2) .
Whisk it well.
Now again add the rest of the milk.
Stir it nicely to avoid lumps.
Now switch on the flame and cook this briefly, till it bubbles slightly.
Stir it from the bottom to avoid the chocolate to get stick to the bottom.
Take it off.
Let it cool for some time.(10 - 15 minutes)
Pour it into the mould.
Deep freeze it for 4 to 6 hours.