How to Make It
Stir together sugar and 1½ cups water in a large heavy-bottomed pot. Place over medium-high and cook, undisturbed, until sugar begins to turn amber around the edge of the pot, about 15 minutes.
Gently stir mixture until color is uniformly amber, about 1 minute more. Reduce heat to low and gradually stir in cream. (Be careful: Sauce will bubble and steam vigorously.) Continue to cook, stirring over low, until caramel is smooth, about 2 minutes.
Add butter, 1 piece at a time, whisking constantly until butter is melted and emulsified.
Remove from heat and stir in vanilla and salt. Serve warm or let cool. Store in airtight containers and refrigerate for up to 3 weeks.
For a sweet holiday gift, place caramel in 4- or 8-ounce glass jars and tie with ribbon.