01 -  Line a 20×20 cm baking pan with parchment paper and preheat the oven to 175°C. 
 02 -  Toast the pecans in a dry skillet over medium heat for 5–7 minutes, stirring often, until fragrant. Let cool. 
 03 -  In a saucepan over low heat, melt the butter and dark chocolate together, stirring until smooth. Remove from heat and let cool slightly. 
 04 -  In a large mixing bowl, whisk the eggs with granulated sugar, brown sugar, vanilla extract, and salt until thick and slightly pale, about 2–3 minutes. 
 05 -  Slowly whisk the melted chocolate mixture into the egg mixture until well combined. 
 06 -  Sift in the flour and cocoa powder. Fold gently until just incorporated, avoiding overmixing. 
 07 -  Fold in the toasted pecans. 
 08 -  Pour the batter into the prepared pan and smooth the top with a spatula. 
 09 -  Bake for 28–32 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet batter). 
 10 -  Cool completely in the pan before slicing into squares.