Line an 8 square pan with parchment paper on both sides.

Warm the butter in the microwave until it’s almost, but not fully melted. Add the sugar then return it to the microwave for 30 seconds (on 100% power). Whisk the sugar and butter together well. Add the cocoa and whisk well.

Add the egg, yolk, vanilla and salt, whisking very well. Stir in the flour and milk. Fold in the chopped chocolate, scraping the chopping board to incorporate all the little chocolate shards.

Transfer the batter to the prepared pan and let set for about 20-30 minutes at room temperature.

Preheat the oven to 350 F.

Bake brownies for about 30 minutes, until a cake tester comes out with a thick batter (like goo, it should not be runny).