Preheat the oven to 350°F. Lightly grease a light-colored 8x8-inch metal pan with cooking spray. Line with parchment paper, leaving an overhang for easy removal. (Avoid foil or wax paper.)
In a large mixing bowl, whisk together melted butter, white sugar, and brown sugar until the sugar dissolves. Add eggs and vanilla, whisking until smooth and creamy.
Add flour, cocoa powder, and salt to the bowl. Switch to a wooden spoon and mix until just combined. Stir in ½ cup mini chocolate chips—do not overmix.
Scrape the batter into the prepared pan and smooth the top. Sprinkle the remaining ¼ cup mini chocolate chips evenly over the surface.
Bake on the middle rack for 25-30 minutes, or until the brownies are just set to the touch. Do not overbake—they will firm up as they cool.
Let brownies cool completely. Using the parchment overhang, lift them from the pan. Cut into squares using a sharp knife. For clean cuts, run the knife under warm water, wipe dry, and repeat between cuts. Sprinkle with flaky sea salt if desired. Enjoy!
Notes
Note 1: Use Dutch-processed cocoa powder for the best texture and flavor. To measure, spoon the cocoa into a measuring cup and level off—packing too much can dry out the brownies.Note 2: Baking time may vary with dark-colored metal or glass pans. Light-colored, shiny pans produce the best results since they heat more evenly.Storage: Store brownies in an airtight container for 4 days at room temp or a week in the fridge for extra fudginess. To freeze, wrap individually and store for up to 3 months—thaw at room temp or microwave briefly.