Add the brown sugar, pure cane sugar and butter slices to a small saucepan.
Stirring frequently, cook on medium low heat until butter is melted and completely combined with the sugar, no separation - about 2-3 minutes.
Add in the vanilla extract and the heavy cream. Stirring frequently, cook for about 5 minutes simmering on medium low heat. It should be starting to thicken and have less liquid. It will thicken more as it cools.
Remove from heat and stir in the salt until mixed in well. It it is too thick while it is hot, put back on the stove with a little water (a Tablespoon at a time) and cook over medium low heat until desired consistency.
It is ready to serve or you can pour into a half pint sized jar to store in the fridge for up to 2 weeks.
It will become solid in the fridge. To reheat simply place back on the stove or heat in the microwave in 10 second intervals until heated through. If needed, you can add a little water to thin it out while heating it.
This makes about 1 cup of caramel syrup and we estimated each serving as 1 Tablespoon. Serving sizes will vary based on what you are using the syrup for.Butter - we recommend unsalted but you can use salted. Depending on how salty you like it, you may want to reduce the amount of salt added. Heavy cream - heavy cream is preferred but can use half and half in it's place.Salt - If you do not usually eat much salt, you can start with a half teaspoon and add more if you like. Be very carefully tasting it and be sure to cool the amount on your spoon before tasting, hot caramel can cause serious burns.