Keep 1/4 cup milk aside.
Boil rest of the milk.
Keep on medium fire for 25 minutes after the first boil.
Remove from fire.
Dissolve cornflour in 1/4 cup milk.
Add cornflour paste into the boiled milk.
Add sugar.
Boil milk.
Cook for 4-5 minutes, stirring continuously, till it coats the spoon and becomes a very thin custard.
Cool slightly.
Soak gelatine in water.
Heat on low flame to dissolve it.
Mix gelatine solution to the lukewarm custard.
Freeze for 3-4 hours, turning the fridge to its coldest.
After the custard is frozen, proceed further.
Beat chilled cream with powdered sugar till slightly thick and fluffy.
Cut the frozen custard into small cubes in a big pan & beat well till smooth and fluffy.
Do not let it melt while beating.
Add the beaten cream to the beaten custard.
Add essence and mix well.
Freeze till partially set.
Cut the chocolate into small pieces.
Spread the chocolate pieces in a plate and keep in the freezer till hard.
Beat the ice cream when partially set and slushy.
Mix in the hard, frozen chocolate pieces.
Freeze ice cream till firm.