In a small, heavy saucepan, pour in enough water to barely cover the bottom of the pan. Add the sugar to the center of the pot, ensuring any crystals that get on the sides of the pan are returned to the water. Add the corn syrup, cover, then bring the mixture to a boil over medium-high heat and cook until the sugar has dissolved, 2 to 3 minutes. Uncover and, without stirring, boil the syrup until it reaches an amber color. (If the mixture begins to crystallize, add a little more water and begin the caramelization process again.) Remove from the heat and immediately swirl in the butter and salt, then add the nuts and stir quickly to coat with a heatproof silicone spatula.