Cookie Ingredients:
1 cup unsalted butter at room temperature
1/2 cup white sugar
1/2 cup dark brown sugar
1 egg
1/4 cup light corn syrup
1 ½ teaspoon vanilla extract
3 cups old fashioned rolled oats
1 ½ cups all purpose flour
1 teaspoon baking soda
1/2 teaspoon table salt
1 package high quality semi-sweet chocolate chips
1/2 cup Vanilla sugar (or raw sugar works too)

Caramel Buttercream Ingredients:
Adapted from Chow

1/2 cup granulated sugar
4 tablespoons water
1/2 cup heavy cream
1 teaspoon vanilla extract
1 1/2 sticks butter, at room temperature
1/2 teaspoon fluer de sel or sea salt
1 cup powdered sugar