Add wine and ½ cup sugar to a medium (2 to 3 quart) saucepan. Bring to a boil over high heat and cook, stirring occasionally, until reduced to ½ cup, about 30 minutes. Remove from heat and add remaining two cups sugar, corn syrup, cream and salt. Stir sauce until smooth.
Return to medium-high heat and cook without stirring until the mixture reaches exactly 240°F on a candy thermometer. If the sides of the pan get burnt or gritty, you can wash them down with a pastry brush dipped in water.
Let caramel cool to thicken, at least 15 minutes. It should be thick enough to coat the edge of an apple without most of it dripping off. Insert a skewer into each apple and dip in the caramel, swirling to coat, letting excess drip back into the pan. Place apples on sheets of parchment paper or nonstick Silpat mats to cool.
