Step 1: Prepare the Brownie Layer

1. Preheat the oven to 350°F (175°C).
2. Line a 9×13-inch baking dish with parchment paper.
3. In a large bowl, whisk together melted butter, granulated sugar, and brown sugar until smooth.
4. Add eggs and vanilla extract, whisking until fully combined.
5. Sift in cocoa powder, flour, salt, and baking powder, mixing until just combined.
6. Pour the batter into the prepared baking dish, spreading evenly.

Step 2: Bake the Brownie Base

1. Bake for 20 minutes, until the edges are set but the center is slightly soft.
2. Remove from the oven and let cool slightly while preparing the pecan topping.

Step 3: Make the Pecan Pie Topping

1. In a medium bowl, whisk together brown sugar, maple syrup, melted butter, vanilla extract, salt, and eggs.
2. Stir in the pecan halves, coating them well in the mixture.

Step 4: Assemble and Bake to Perfection

1. Pour the pecan pie filling evenly over the partially baked brownies.
2. Return to the oven and bake for 20-25 more minutes, until the topping is set and slightly bubbly.
3. Remove from the oven and let the brownies cool completely before slicing.

Step 5: Serve and Enjoy!

1. Cut into squares and serve as-is or with a scoop of vanilla ice cream.