Line a 9-inch square pan with parchment or wax paper, allowing the paper to drape over the sides; spray lightly with cooking spray.
In 1-quart saucepan, heat butter, whipping cream, whiskey, vanilla and 1/4 teaspoon salt to a boiling, stirring frenquently. Remove from heat; set aside.
In 3-quart saucepan, mix sugar, corn syrup and water. Heat to boiling over medium-high heat. DO NOT STIR. Boil until sugar turns a warm golden brown.
When sugar mixture is done, turn off the heat and slowly add the cream mixture to the sugar mixture. BE CAREFUL - it will violently bubble up. Cook over meduim-low heat for about 10 minutes, until mixture reaches 248 degrees F on a candy thermometer. Pour caramel into prepared pan; cool for 10 minutes. Sprinkle with 1 Tbsp. kosher salt; cool completely.