Preheat the oven to 350°F and line a 9×13 pan with parchment paper or coat with cooking spray.
Simmer butter in a saucepan until it crackles and turns golden brown, then remove from heat.
Mix flour and dry ingredients in a bowl, then set aside.
Blend browned butter, shortening, sugar, eggs, and extracts using a mixer, then incorporate sour cream.
Add the flour mixture to the wet ingredients and blend until well combined (the dough will be thick).
Spread the batter evenly into the prepared pan and bake at 350°F for 25-35 minutes, until golden.
Let the cookie bars cool before frosting.
For the frosting, cook brown sugar, butter, and cream over low heat, then increase the heat to medium and cook for 5 minutes until caramel forms. Mix in powdered sugar and sea salt, then frost the cooled cookies and sprinkle with extra sea salt.