Special equipment: Blender Medium saucepan
Pour 1/3 cup water and the bourbon into a medium saucepan and set over high heat. Carefully pour the sugar directly into the center so none of it splashes up the sides of the pot. Bring to a boil and cook until the sugar starts to turn brown. Do not stir the pot. If you need to, gently swirl the pot to help melt all the sugar.
Once the sugar turns a rich, deep brown, remove the pan from the heat and carefully pour in the cream, taking care as it will splatter a little. Add the butter, salt, and vanilla. Swirl the pot until the butter dissolves completely and evenly into the caramel sauce-this makes it shiny and rich.
Drizzle a little of the caramel sauce into 2 tall milkshake glasses. Combine the ice cream, milk, and the remaining caramel sauce in a blender, reserving a little of the caramel for the topping. Blend until smooth and pour into the glasses. Top each with a little whipped cream, a pinch of sea salt, and a drizzle of the reserved salted caramel sauce.
Prep-Ahead Tip: Make the salted caramel up to a week ahead of time. In fact, make a big batch of it and keep it in your refrigerator. It goes great with just about any dessert: apples, ice cream, chocolate cake, bananas . . . you name it.
Copyright 2014 by Guy Fieri, by arrangement with HarperCollins Publishers