1. Preheat the oven to 350°F. Grease a 9-inch square baking pan and line it with parchment paper so that it hangs over two sides to make it easy to life the brownies out of the pan when baked.
2. Melt the chocolate with butter in a medium heatproof bowl over a pan of simmering water. Make sure the bottom of the bowl does not touch the water, or you will burn the chocolate. Whisk until melted and smooth. Remove from heat and add sugars into the chocolate mixture and whisk until completely combined. Let the chocolate mixture cool for a few minutes.
3. Add in eggs and vanilla, and beat with a hand mixer on medium speed for 2 minutes.
4. Add in flour, cocoa powder, and salt and fold together using a large silicone spatula until just combined. Transfer the thick batter into the prepared baking pan.
5. Bake for 20 minutes. The brownies won’t be fully cooked, but the top should start to set. If the brownies look completely wet and raw, bake for another 5 minutes, or until it starts to set.

Make the pecan pie topping:

1. While the brownie base is baking, prepare the pecan pie topping. In a large mixing bowl, whisk together brown sugar, maple syrup, melted butter, egg, vanilla, and salt until smooth and combined. Stir in the whole and chopped pecans until coated.
2. Pour the topping over the baked brownie immediately once the brownie is removed from the oven and is still hot. Return the baking pan back into the oven and bake for another 15-20 minutes until the topping has set (it may jiggle a little with no liquid visible in the topping).
3. Allow the pecan pie brownies to cool completely in the pan on a wire cooling rack. Once cooled, you can place the brownies in the refrigerator for 1-2 hours for easier slicing, if you prefer. Once cooled completely, easily lift it out of the pan using the parchment paper overhang. Then, slice into 16 squares and serve.