Pre-heat the oven to 350ºF. Grease an 8×8” or 9×9” pan with butter. Line the pan with parchment paper and lightly butter the parchment, or spray with oil.
Melt the butter and 1 cup of semi-sweet chocolate in a large bowl. I like to use a large glass bowl and microwave it in 30 second intervals, stirring in between, until fully melted and smooth.
Add the granulated sugar and brown sugar to the melted chocolate mixture and whisk until incorporated.
Add the eggs one at a time, whisking well after each addition.
Add the vanilla extract and whisk to combine.
Sift together the flour, cocoa powder, and salt in a medium bowl. Add to the batter and whisk until incorporated.
Fold in the remaining 1 cup of chocolate chips with a spatula.
Pour ⅔ of the brownie batter into the prepared pan and spread evenly.
Spoon the dulce de leche over the batter and gently spread it out, leaving a little border around the edges.
Top with the remaining brownie batter and carefully spread it over the dulce de leche layer.
Sprinkle the extra chocolate chips on top.
Bake in the pre-heated oven for about 42 to 50 minutes, until the edges are set and the center no longer looks raw.
Let the brownies cool completely before slicing for cleaner layers.
