Preheat the oven to 350°F / 175°C. Grease and line a 8" square pan with butter and parchment paper.
In a large microwaveable mixing bowl (or in a medium sized saucepan set over medium heat), melt together the chocolate and butter.
Once the mixture is melted, immediately whisk in the cocoa powder and sugar.
In a separate bowl, whisk the eggs and sugar together until the mixture is light and foamy.
Gently fold the melted chocolate mixture into the egg mixture until fully combined.
Add in the flour and salt and gently mix the mixture together just until no flour streaks remain.
Pour the brownie batter into the prepared pan and smooth it out to an even layer. Bake the brownies for 20 minutes, until the top has slightly set. In the meantime, make the pecan pie filling
Pecan Pie Filling
In a medium sized microwave safe bowl, melt the butter. Add in the sugar, syrup, salt, vanilla, and egg. Whisk until well combined, then whisk in the pecans.
Once the brownies have slightly set, remove them from the oven. Gently pour the pecan pie filling over the brownies into an even layer.
Return the brownies to the oven and continue baking for 25 minutes, until the pecan pie filling has browned and only wobbles slightly in the middle.
Wait for the brownies to fully cool before cutting. Serve and enjoy!