Prep Oven & Pan: Preheat oven to 350°F (175°C). Line an 8x8-inch or 9x9-inch metal square baking pan with parchment paper, leaving a 2-inch overhang on the sides for easy lifting.

Melt Chocolate Base: In a heatproof bowl set over a saucepan of simmering water (or in microwave at 50% power in 30-second bursts), melt butter and chopped dark chocolate together until glossy and smooth. Let cool 5 minutes.

Beat Eggs & Sugar: Whisk granulated sugar and dark brown sugar into warm melted chocolate. Whisk in eggs one at a time, followed by vanilla extract, beating vigorously for 1 minute until shiny and glossy.

Fold Dry Ingredients: Sift in cocoa powder, all-purpose flour, and sea salt. Fold gently with a silicone spatula just until no dry flour pockets remain. Do not overmix.

Par-Bake Brownie: Spread thick batter evenly into the prepared pan. Bake at 350°F (175°C) for 18 to 20 minutes until the top is set but the center remains slightly underbaked.

Simmer Pecan Pie Topping: While brownie bakes, whisk melted butter, brown sugar, pure maple syrup, heavy cream, vanilla, and salt in a small saucepan over medium-low heat for 2 minutes until sugar dissolves and sauce bubbles gently. Stir in chopped pecans and pecan halves.

Assemble & Finish Bake: Remove par-baked brownie from the oven. Immediately pour warm gooey pecan mixture over the top, using an offset spatula to spread evenly to all four corners. Return to oven and bake for an additional 15 to 18 minutes until pecan topping is bubbling vigorously around the edges.

Cool Completely & Slice: Sprinkle top with flaky Maldon sea salt. Allow bars to cool completely to room temperature in the pan for 2 hours, then chill in the refrigerator for 1 hour for clean, razor-sharp bakery slices. Lift out using parchment handles, cut into 16 decadent squares, and enjoy!