11 oz sugar
½ teaspoon sea salt (do not use table salt)
8 fl oz heavy cream
16 fl oz whole milk
1 tbs cornstarch
1 teaspoon vanilla extract
Note: Controlling temperature is important in this recipe. If you add the rest of the dairy too early, you'll boil off all the water in it.
Use a heavy based saucepan with deep sides (the cream foams up). You need a light color pan (i.e. not non-stick) to accurately assess the caramel's color.
Weigh out the sugar, add the salt, and add just enough water to wet it evenly (like wet sand).
Measure out the cream and have it standing by.
Heat the sugar over medium heat tilting the pan occasionally in a rotating swirling motion so the sugar cooks evenly.
When it starts to turn golden brown turn the heat down to medium low, and swirl continuously.
When it is dark amber, remove from the heat, and immediately start to SLOWLY add the cream, stirring continuously with a whisk. BE CAREFUL, it will boil aggressively.
Keep stirring until it stops boiling, then set aside to cool for a few minutes (we don't want the milk to boil when we add it).
Measure out the milk in a saucepan, steal a tablespoon or two to make a slurry with the cornstarch in a saucer, and heat the milk over medium-low heat to a simmer.
Add the cornstarch slurry to the simmered milk, stirring vigorously. Allow to cool.
Add the thickened milk and vanilla; stir well to combine.
Refrigerate for at least 4 hours. Freeze for an hour, stirring occasionally.
Process in an gelato or ice-cream maker, then transfer to an airtight container and put it back in the freezer to firm up.
Footnote: It's difficult to get the caramel to freeze well. If you use milk instead of cream, the mixture breaks. Could possibly try less cream.
http://www.gourmet.com/recipes/2000s/2009/08/salted-caramel-ice-cream