In a pan take water and bring it to boil, place a bowl in the boiling water and add chocolate to the bowl.
Let the chocolate melt properly.
Remove the chocolate bowl from the pan. Place another bowl on the top of pan and add 4 egg whites.
Add sugar to the egg whites, and blend.
Remove the bowl from the pan and blend the egg white more till it gets fluffy in texture.
In a pan take boiling water, and place a bowl on the top of it with egg yolks in it.
Blend egg yolks properly.
Add melted chocolate in beaten egg yolks and mix properly.
Start adding beaten egg whites in the mixture little by little and mix.
Add half cup of water to the mixture and mix properly.
Pour mousse in the glass and let it chill for 1 hour.