8 tablespoons unsalted butter, cut into pieces
6 ounces bittersweet chocolate, chopped (I used Ghirardelli bittersweet chips)
1/4 cup unsweetened Dutch-process cocoa powder
3 large eggs
1 cup sugar
1 teaspoon vanilla extract
1 cup flour
1 cup Dulce de Leche
Preheat the oven to 350 degrees.
Line a 8-inch square pan with a long sheet of aluminum foil that covers the bottom and reaches up the sides. If it doesn't reach all the way up and over all four sides, cross another sheet of foil over it, making a large cross with edges that overhang the sides. Grease the bottom and sides of the foil with a bit of butter or non-stick spray.
Melt the butter in a medium saucepan. Add the chocolate pieces and stir constantly over very low heat until the chocolate is melted. Remove from heat and whisk in the cocoa powder until smooth. Add in the eggs one at a time, then stir in the sugar, vanilla, then the flour.
Scrape half of the batter into the prepared pan. Drop one-third of the Dulce de Leche, evenly spaced, over the brownie batter, then drag a knife through to swirl it slightly. Spread the remaining brownie batter over, then drop spoonfuls of the remaining Dulce de Leche in dollops over the top of the brownie batter. Use a knife to swirl the Dulce de Leche slightly.
Bake for 35 to 45 minutes. The brownies are done when the center feels just-slightly firm. Remove from the oven and cool completely.