Preheat the oven to 350 degrees F. Butter and flour a 9 x 12 x 1 1/2-inch baking pan.
Melt the butter, 8 ounces of the chocolate chips and the unsweetened chocolate together in a medium bowl set over simmering water. Allow to cool for 15 minutes. In a large bowl, stir (do not beat) together the eggs, coffee, vanilla and sugar. Stir the chocolate mixture into the egg mixture and allow to cool to room temperature. (It is very important to allow the butter to cool before adding the chocolate chips, or the chips will melt and ruin the brownies.).
In a medium bowl, sift together 1/2 cup of the flour, the baking powder and salt and add to the chocolate mixture. Toss the remaining 6 ounces of chocolate chips and the remaining 2 tablespoons of flour in a medium bowl and add them to the chocolate mixture. Spread evenly in the prepared pan.
Bake for 35 minutes, until a toothpick comes out clean. Don't overbake!
As soon as the brownies are out of the oven, place the jar of caramel sauce without the lid in a microwave and heat just until it's pourable. Stir until smooth. Drizzle the caramel evenly over the hot brownies and sprinkle with the sea salt. Cool completely and cut into 12 bars.