Preheat oven to 350°F. Line a 9-inch baking dish with parchment paper. Set aside.
In a medium saucepan, melt butter over medium heat. Remove from heat and stir in chocolate morsels and granulated sugar until chocolate is completely melted.
Add eggs one at a time, stirring completely after each addition. Stir in 1 teaspoon vanilla extract.
Add cocoa powder, flour, kosher salt, and baking powder. Stir just until combined; do not overmix.
Pour batter into prepared baking dish and bake for 20 minutes. While brownies bake, prepare the pecan pie topping.
In a medium bowl, whisk light corn syrup, maple syrup, dark brown sugar, 1 large egg, and 1 teaspoon vanilla extract until smooth.
Stir pecan halves into the syrup mixture until fully coated.
Spread pecan mixture evenly over the partially baked brownies. Bake for an additional 25 to 30 minutes, or until a knife inserted near the center comes out mostly clean.
Cool brownies completely on a rack before slicing and serving.
Notes
Store brownies in an airtight container at room temperature for up to 5 days or refrigerate. Brownies can also be frozen for up to 3 months.