Salted Caramel Frosting

This came from the Brooklyn Kitchen Blog, and it's actually part of a recipe for cupcakes, but this frosting is quite possibly, the best frosting I have ever made. Ever.

Salted Caramel:

4 tablespoons water
1 cup sugar
2 tablespoons light corn syrup
1/2 cup heavy cream
2 tablespoons butter
1/2 teaspoon lemon juice
1/2 teaspoon salt, kosher or sea

Combine the water, sugar, and the corn syrup in a deep saucepan and cook over medium heat—stir with a wooden spoon to combine
Cover the saucepan and let it cook over medium/medium-low heat for 3 minutes.
After 3 minutes, remove the lid, increase the heat to medium-high, and bring to a boil.
(Do not stir from this point on, but once it starts to turn brown at the edge you should carefully shake/swirl the pan so that one area of the caramel doesn’t burn.)
Continue to cook until the caramel turns an even amber color then remove from the heat and let stand for about 30 seconds.
Pour the heavy cream into the mixture. Be careful. The mixture will bubble up!
Stir the mixture. Add the butter, lemon juice, and salt. Stir until combined.
Pour into a Pyrex measuring cup.
Stirring occasionally, allow to cool until thick and warm, about 20 minutes.

Frosting:

1.5 sticks butter at room temperature
6 ounces cream cheese
4-5 cups powdered sugar
3/4 cup salted caramel

Beat butter and cream cheese at medium speed until creamy.
Sift 2 cups of powdered sugar into the cream cheese mixture and beat to combine.
Add 3/4 cup of the salted caramel and beat to combine.
Sift rest of powder sugar, in 1 cup increments and beating between each, until you arrive at the thickness and sweetness you desire.