Preheat oven to 350°F. Line two baking sheets with parchment paper and set aside.
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter and sugars until creamy. Add the egg and vanilla and beat until fluffy.
In a large bowl, whisk together the flour, oats, baking soda, cinnamon and salt.
Gradually, add the dry ingredients to the butter mixture and beat until well combined.
Stir in the caramel bits until evenly distributed.
Using a small cookie scoop, scoop two-teaspoon size portions of dough onto the prepared cookie sheets a few inches apart from each other. Using the bottom of a lightly greased glass, press each scoop of dough until it’s flat and about 2 inches in diameter. Sprinkle each cookie with a pinch of sea salt.
Bake 10-12 minutes or until cookies are just starting to brown. Transfer cookies to a wire rack to cool completely.
While cookies are cooling, prepare the caramel filling. In the bowl of an electric mixer fitted with the whisk attachment, beat the butter and caramel topping until smooth. Add the sea salt and then the powdered sugar, one cup at a time, until well combined. Turn the mixer speed to high and beat the filling until thick and fluffy, about 2 minutes.
Turn half of the cookies over and spread with the filling. Top with a similar size cookie.