Using an electric mixer with a whisk attachment, or a regular whisk and lots of arm power, whisk together the nescafe powder, sugar and hot water.
Keep whisking and whisking and the mixture will become thick and foamy, and eventually stiff, almost like egg whites. Once it becomes so stiff, it won't drop off a spoon, you're ready!
Pour cold milk into two glasses, add ice cubes if you like, and place a large dollop of coffee mousse in each glass. Before drinking, stir it a little. Enjoy!