Instructions

to make the caramel

Combine cream and salt in small bowl; stir well to dissolve salt. Combine water and corn syrup in heavy-bottomed 2- to 3-quart saucepan; pour sugar into center of saucepan, taking care not to let sugar granules touch sides of pan. Gently stir with clean spatula to moisten sugar thoroughly. Cover and bring to boil over medium-high heat; cook, covered and without stirring, until sugar is completely dissolved and liquid is clear, 3 to 5 -minutes. Uncover and continue to cook, without stirring, until bubbles show faint golden color, 3 to 5 minutes more. Reduce heat to medium-low. Continue to cook (swirling occasionally) until caramel is light amber and registers about 360 degrees on candy or instant-read thermometer, 1 to 3 minutes longer. Remove saucepan from heat and carefully add cream to center of pan; stir with whisk or spatula (mixture will bubble and steam vigorously) until cream is fully incorporated and bubbling subsides. Stir in butter and vanilla until combined; transfer caramel to microwaveable measuring cup or bowl and set aside.

to make the brownies

Adjust oven rack to lower-middle position; heat oven to 325 degrees. Lightly spray 9-inch-square baking pan with nonstick cooking spray. Cut 14-inch length extra-wide heavy-duty foil; fold cut edges back to form 8 1/2-inch width. With folded sides face down, fit foil securely into bottom and up sides of baking pan, allowing excess to overhang pan sides. Spray foil with cooking spray.
Microwave butter, bittersweet chocolate, and unsweetened chocolate in bowl at 50 percent power, stirring occasionally, until melted and smooth, 2 to 4 minutes; set aside and let cool slightly. Meanwhile, whisk together flour and baking powder in small bowl; set aside. Whisk eggs in large bowl to combine; add sugar, vanilla, and salt and whisk until incorporated. Add cooled chocolate mixture to egg mixture and whisk until combined. Using rubber spatula, stir in flour mixture until almost combined. Stir in chopped pecans and chocolate chips, if using, until incorporated and no flour streaks remain.
Following illustrations below, spread half of brownie batter in even layer in prepared pan. Using greased ¼-cup dry measuring cup, drizzle ¼ cup caramel over batter. Using spoon, dollop remaining batter in large mounds over caramel layer and spread into even layer. Drizzle another ¼ cup caramel over top. Using butter knife, swirl brownie batter through caramel. Bake until toothpick inserted in center comes out with few moist crumbs attached, 35 to 40 minutes, rotating pan halfway through baking. Let brownies cool completely in pan on wire rack, about 1 ½ hours.
Heat remaining caramel (you should have about 3/4 cup) in microwave until warm and pourable but still thick (do not boil), 45 to 60 seconds, stirring once or twice; pour caramel over brownies. Using spatula, spread caramel to cover surface. Refrigerate brownies, uncovered, at least 2 hours.
Using foil extensions, lift brownies from baking pan, loosening sides with paring knife, if needed. Peel away and discard foil. Using chef's knife, cut brownies into 25 evenly sized squares. Press a pecan half onto surface of each brownie. Serve chilled or at room temperature.