Combine the sugar and butter in a medium sized saucepan. Melt on medium heat, then bring to a bubbling boil, letting the sugar darken somewhat. Do not boil until it's hard candy however.
Once the butter and sugar have started bubbling, let boil for another 2-3 minutes, then slowly and carefully pour in the hot water. It most likely WILL SPIT so be careful!
Stir together and bring to a boil again.
To thicken, combine the cornstarch and cold water, then whisk into the boiling brown sugar mixture. Cook until it thickens up slightly then remove from the heat.
Serve warm.
Notes
You can easily double this recipe if you are feeding a large crowd in the mornings.
This will keep in your refrigerator for a solid 4-5 days, just simply reheat and stir and it will all come together again