Using a spoon spread the caramel sauce on the inside of 2 glass and around the rims. Stick the popcorn and pretzels to the outside, using more sauce as glue if necessary and put the glasses in the fridge so that the sauce hardens and the popcorn and pretzels stick.
To make the milkshakes
Add the ice-cream, milk and salted caramel sauce to a blender and blend until combined. Add enough milk to fill your glasses.
Pour into the prepared glasses, top with another scoop of ice-cream, more popcorn and salted caramel sauce and serve immediately.