Preheat the oven to 350°F. Grease an 8x8 or 9x9 pan. For easy removal of the brownies, place parchment paper on the bottom and 2 sides of the pan. Grease again and then set aside.
Melt the butter using a double boiler method. When it's really hot, stir in the sugar. Continue whisking until it turns glossy. Remove from heat and allow to cool for 5 minutes.
1 1/4 cups butter, 2 cups light brown sugar
Whisk in one egg at a time, and then the vanilla.
4 eggs, 1 tbsp vanilla
Fold in the dark cocoa powder and unsweetened cocoa powder. Make sure you don't over mix.
1 cup unsweetened cocoa powder, 1/2 cup dark cocoa powder
Add in the flour and salt and continue mixing.
1/2 tsp salt, 2/3 cups flour
Add in the Oreos and chocolate chips.
14 Oreos, 1/3 cup milk chocolate chips
Pour into a prepared pan. Top off with extra Oreos if desired. Bake for 40-50 minutes depending on your oven. Start checking after 38 minutes. The brownies will have set edges and the middle will look a little underbaked. When you insert a toothpick it'll come out with moist crumbs.
Allow to cool completely. The brownies bake as they cool so if you slice before this, the brownies will fall apart. If you don't mind this then go for it! I prefer mine served warm with a scoop of vanilla ice cream.
If you have any leftovers, which I highly doubt, store in an airtight container on the counter or in the fridge for up to 1 week or individually wrapped in the freezer for up to 3 months!