1. Preheat oven to 325 degrees F. Line a 9 by 13 inch pan with parchment paper.
2. Place semisweet chocolate, unsweetened chocolate, and butter in a large, microwave safe bowl and microwave on high for 2 minutes. Remove bowl from microwave and stir until chocolate has melted completely. If additional melting is needed, microwave at 20 second intervals, stirring well after each one.
3. With a wooden spoon, beat sugar and eggs into chocolate mixture. Stir in flour.
4. Pour batter into prepared pan and spread it evenly. Bake for 25 to 28 minutes, or until the top looks set and a knife comes out clean. Cool pan on a rack.
5. While brownies are baking, start making caramel. In a medium saucepan, stir together sugar, water, and corn syrup. Cook over medium high heat without stirring until mixture turns deep amber, about 15 to 25 minutes. Be patient! How quickly the sugar caramelizes can depend on the pan, heat source, and weather, but it will caramelize.
6. Turn heat to low and add butter and heavy cream. There will be a lot of splattering, so be careful; wear oven mitts to protect your hands and wrists. When splattering dies down, stir caramel until butter is fully melted. Remove from heat. Caramel will still be bubbling. Keep stirring until it's completely smooth. Allow caramel to cool for about 10 minutes.
7. Spoon caramel onto cooled brownies and spread evenly with a spatula, so caramel completely covers brownies. (you may have a little extra caramel. It's great drizzled on ice cream; just heat it for a few seconds in the microwave.) Immediately sprinkle pecans over top then press down slightly. Before cutting into 24 bars, wait to caramel to cool completely and set, at least an hour, preferably two. Store in an airtight container at room temperature for up to five days or freeze for up to a month. If you're going to freeze the brownies, don't cut them into squares until you thaw them.
Source: Hannaford fresh Magazine, May - June 2007