Dulce De Leche Brownies (adapted from David Lebovitz)
Preheat your oven to 350 degrees and line an 8×8 baking dish with aluminum foil.
Place your butter in a medium saucepan set over medium heat and melt. Add your chocolate and continue cooking over medium heat, stirring often, until your chocolate is completely melted. Turn off the heat and whisk in your cocoa powder. Add your eggs, one at a time, whisking immediately and vigorously to prevent them from cooking before becoming fully incorporated. Finally, mix in your walnuts, sugar, vanilla and then your flour.
Pour half of your batter into the baking dish. Drop half of your dulce de leche onto the batter. Swirl the dulce de leche to spread it out slightly. Pour your remaining brownie batter over the dulce de leche swirls. Drop your remaining dulce de leche over the top and again swirl.
Bake the brownies for 35 to 45 minutes until the center is just set, then remove from the oven. Allow them to cool in the dish for 5 to 10 minutes and then lift the brownies and foil out of the dish and place on a wire rack to finish cooling.