Add the instant coffee, sugar, and hot water to a small cup. Stir well until the coffee dissolves completely. If you like your coffee thick you can beat the mixture with a coffee beater.
Add the white chocolate sauce to the warm coffee and stir until smooth.
Take a tall glass and fill it with ice cubes to the top.
Pour the cold milk over the ice.
Slowly pour the white chocolate coffee mixture over the milk to create beautiful layers.
Mix everything together, top with whipped cream if desired, and serve immediately.