Line an 8x8 inch pan with parchment paper. In a medium saucepan, combine sugar, corn syrup, and water. Cook over medium heat, stirring, until sugar dissolves. Stop stirring and cook until the mixture turns an amber color.

Remove from heat and carefully whisk in the warm heavy cream. Stir in the butter, vanilla, and fine sea salt until smooth. Pour into the prepared pan and let it cool completely until firm, about 2-3 hours.

Place 8 oz of the chopped dark chocolate in a heatproof bowl. Heat 1 cup of heavy cream until simmering, then pour over the chocolate. Let stand for 5 minutes, then stir until smooth and glossy. Let the ganache cool until it's firm enough to scoop (about 1 hour in the fridge).

Once firm, cut the caramel into small squares and roll them into balls. Scoop a portion of ganache, flatten it in your palm, place a caramel ball in the center, and wrap the ganache around it. Roll into a smooth ball. Place on a parchment-lined baking sheet and chill for 30 minutes.

Melt the remaining 8 oz of dark chocolate. Dip each chilled truffle into the melted chocolate, coating it completely. Lift out with a fork, letting excess chocolate drip off. Place back on the parchment paper and immediately sprinkle with flaky sea salt. Let set completely before serving.