1. Preheat your oven to 350 degrees.

To prepare the brownies.

1. Weigh or lightly spoon flour into dry measuring cups, and level with a knife. Combine the flour, and the next 4 ingredients (through baking powder) in a large bowl, stirring well with a whisk.
2. Combine 6 tablespoons butter, eggs, and 1 teaspoon vanilla extract. Add this mixture to the flour mixture, stir to combine.
3. Scrape the batter into a 9-inch square metal baking pan lightly coated with cooking spray.
4. Bake at 350 degrees for 19 minutes, or until a wooden pick inserted comes out with moist crumbs clinging.
5. Cool in pan on a wire rack.

To prepare the topping:

1. Melt 1/4 cup butter in a saucepan over medium heat. Add the brown sugar, 1 1/2 tablespoons milk, and cook 2 minutes.
2. Remove from the heat, and add vanilla and powdered sugar, and stir with a whisk until smooth. Spread this mixture evenly over the cooled brownies and let stand 20 minutes, or until set.
3. Combine the remaining 2 tablespoons milk, and chocolate in a microwave-safe bowl, and microwave on high for 45 seconds, or until melted, stirring after 20 seconds. Stir just until smooth, and drizzle over the caramel.
4. Sprinkle with sea salt, let stand until set, and cut into 20 squares.