Pre-heat oven to 350°F. Line a 9X9 inch pan with aluminum foil, grease, and set aside.
In a small saucepan, melt butter and chocolate, stirring frequently. This will take 5 or so minutes.
Pour into a large bowl, and mix in the sugars until no lumps remain.
Add eggs and mix, one at a time. Stir in the vanilla.
In a separate small bowl, combine the flour and baking powder. Stir into the butter mixture until completely combined.
Fold in the chopped Twix bars. Scrape batter into pan.
Dot the caramel sauce evenly, swirl with a knife. Sprinkle brownies with sea salt.
Bake for 30-40 minutes, until a toothpick comes out cleanly.
Cool completely and cut into 9 pieces.