Preheat the oven to 300ºF.
Spread the cornflakes on a parchment-lined baking sheet. Bake for 15 minutes until lightly toasted.
Once the cornflakes are cool, transfer them to a big bowl and pour the milk over top. Let steep 20-30 minutes.
Strain the mixture and press gently on the cornflakes to wring out all the milk, being careful not to push too hard (this will push the cornflake mush into the milk, and that's not what you want!).
Add the brown sugar and salt and mix until thoroughly combined.
To make the lattes: fill a large glass with ice. Pour 2 shots of cooled espresso over top, then top with the cereal milk. Garnish with whipped cream if you like!