Add milk and sugar to a non-stick sauce pan then whisk.
Heat the sauce pan to medium. Bring to a simmer, then turn down the heat to low (not medium-low) and leave uncovered. Cook for 40-50 minutes or until thickens. Remove the pan from the heat and let cool. Then transfer the contents to an airtight container for storage until ready to use.Important note: Make sure to stir the milk frequently, this will prevent the condensed milk from turning brown or scorching.