Add the instant espresso, water, & sugar to a medium bowl. Whip with an electric hand mixer for 3-5 minutes, until mixture is fluffy & a lighter brown color closer to caramel.
Drizzle the caramel syrup on the inside of the two glasses you will use. To do this, tilt the cup & turn as you drizzle the caramel up & down the sides. Add the ice & milk to the cup.
Spoon the whipped espresso over the milk, half in each cup. Add a big pinch of sea salt over the coffee (almost a full turn on a grinder). Gently stir the coffee & milk together until they are no longer separated.
I use hot water from my tap, but if you want to warm it up in the microwave that works too. It doesn't need to be boiling hot.
If you're skeptical about the salt, make it without first. Stir together well & taste test it before adding the salt. Start with a small pinch & add another if you still taste a bitter or burnt coffee taste.
Whole Milk or Vitamin D Milk makes this very smooth & silky. I have not tried 2% or Skim milk so I cannot speak to the consistency.