Dulce de Leche Brownies

Line a baking pan with tin foil over the bottom and up all the sides. Grease it well with butter.

Preheat the oven to 350 degrees.

Melt the chocolate pieces and butter (cut into small pieces) over a gently simmering double boiler. Stir somewhat constantly until the chocolate is totally melted, remove from heat and whisk in the cocoa powder. Add the eggs one at a time, followed by the sugar, vanilla, and flour, whisking in between each addition. If using nuts, fold them into the batter.

Spread half of the brownie batter into the pan. Drag lines of Dulce de Leche over batter, top with remaining of the brownie batter, and drop plops of the Dulce de Leche throughout. Swirl it about with a knife to make it look a bit nicer and spread it a little more evenly throughout the dish.
Bake the brownies for 45 minutes. Remove from oven, let cool before removing from pan. Cut and enjoy!