Place sugar in a heavy bottom medium-size pot (it should be at least 2 quarts to prevent sauce from boiling over the top). I like to use a pot with a wide opening as the sugar will melt faster and the sauce will cook a bit quicker.) Cook over medium heat, stirring frequently with a fork till small lumps begin to appear. This will a minute or two. Once the small lumps appear, stop stirring (if you continue to stir it can cause the sugar to crystalize) and reduce heat to medium low. Continue to cook, allowing sugar to melt. It will usually start around the edges and in the center and you'll notice a amber colored liquid forming.

Continue to cook for a few more minutes until most of the sugar has been melted. Watch it carefully and swirl the pot occasionally to evenly melt the sugar. When almost all of the sugar is melted, remove from heat and swirl a few times to finish the melting process. Carefully add the buttermilk, cream, syrup and butter. The mixture will spatter a bit when you add the liquid so be careful. Don't worry, the melted sugar will harden and turn quite gloppy at this point.

Return pot to the stovetop and cook, stirring continuously over medium heat until sugar is melted again and mixture is smooth. This will take a minute or two.

Bring mixture to a boil, then reduce to a steady simmer and cook for 8-10 minutes, stirring frequently. Watch careful and reduce heat if sauce starts boiling too fast and rising up sides of pan. You may have to play with the temperature a bit to maintain a steady simmer but not allow it to boil over. Mixture should be syrupy when finished but will thicken up more as it cools.

Add vanilla, stir well and allow to cool in pot for 20 minutes, then transfer to a airtight glass jar or storage container. Will keep for a week to 10 days in the refrigerator.