Makes about 4 dozen caramels, depending on size
1/2 cup (1 stick) unsalted butter
1 1/4 cups turbinado sugar
1/2 cup heavy cream
1/3 cup light agave nectar
1 1/2 teaspoons coarse sea salt, plus more for sprinkling*
2 teaspoons dark rum (optional)
1 1/2 teaspoons vanilla bean paste or extract
Line an 8x8 inch baking pan with aluminum foil/parchment paper and spray it generously with nonstick cooking spray.
In a heavy medium saucepan over medium high heat, melt together the butter, sugar, cream and agave nectar. Bring it to a boil, stirring until the sugar is dissolved. Clip a candy thermometer to the pot and reduce the heat to low, stirring occasionally, until the caramel reaches 248 degrees (this can take anywhere from 20 to 40 minutes or maybe longer--don't rush it). As you see the temperature creeping towards 248, stir in the salt and the rum. When the caramel hits 248, pull the pot from the heat and stir in the vanilla.
Pour the caramel into the prepared pan set over a wire rack and let it cool, undisturbed, at room temperature overnight, or if you're in a rush, 30 minutes at room temperature and another 30 minutes or so in the refrigerator until the caramel is very firm.
Line a cutting surface with a sheet of parchment paper and turn the caramel slab out onto it. Use a large sharp knife to cut the caramel into neat, even pieces (I like mine to be about 1 x 1 1/2 inches). Lightly sprinkle the caramels with more sea salt and wrap them in squares of parchment or waxed paper. Store at room temperature.
*Try to use the best coarse salt you can get your hands on here--avoid table salt at all costs (in addition to subpar flavor, it doesn't measure the same as coarse salt). In a pinch, you can use kosher, but I really recommend a nice crunchy, crumbly fleur de sel, particularly for sprinkling.
Such a great recipe!!! The caramels are not too sticky, not too hard, and have a great flavor! I opted not to add the sprinkle of salt on the top, because they seemed salty enough without! And I used a pizza cutter to cut, which seemed easier than a knife.