Place a pudding bowl in the refrigerator (A mousse will set fast in a chilled bowl, to yield a uniform spongy texture).
Soak gelatin in 2 tbsp of water.
Beat the yolks with 3/4 cup sugar till light and creamy. Mix corn flour with milk and pour over the egg yolks. Mix well and cook and stir on a low flame till the custard begins to boil (avoid over cooking).
Dissolve the gelatin over a low flame (avoid boiling) and add to the custard. Add essence and allow to cool.
Mix the Chikoo pulp with the custard.
Whip the cream over a bowl of ice till thick. Reserve one and a half cup of whipped cream for topping. Gently mix the rest with the Chikoo custard.
Beat the egg whites till stiff. Add the remaining sugar, little at a time, beating well after each addition. Gently fold the whites into the above mixture. Pour in the chilled pudding bowl and leave in the refrigerator to set.
Serve decorated with the reserved cream and Chikoo slices.