Heat a heavy bottom pan, over medium-high heat add sugar and boil 3 minutes or until sugar melts and liquid is clear, stir pan occasionally and boil 1 minute.
After that add butter and mix well.
Now add full cream and whisking constantly, over low heat 1 minute or until smooth.
Remove the pan from heat add vanilla extract and sea salt (if you use salted butter then no need to add salt), mix well. Transfer to a serving bowl or pitcher. Chill, covered, up to 1 week.