Preheat + prep
Preheat oven to 350°F. Grease an 8x8 baking dish.
Melt butter in a saucepan over medium heat. Cook until golden brown and nutty.
Immediately pour over the 1 cup chocolate chips. Let sit 1 minute, then stir until smooth.
In a separate bowl, whisk sugar, brown sugar, eggs, and vanilla until slightly thickened and glossy (about 1–2 minutes).
Slowly pour the warm chocolate mixture into the egg mixture while whisking.
Stir in flour, cocoa powder, and salt until just combined. Fold in additional chocolate chips.
Pour into prepared dish and bake for 35–40 minutes.
Let sit 10–15 minutes. Scoop and serve warm.