1) Preheat the oven to 350 degrees.Grease a 13X9 baking dish.In a saucepan melt butter and 1 cup semi-sweet chocolate, stirring constantly over very low heat until the chocolate is melted. Stir in eggs one at a time, then stir in the sugar, vanilla, espresso powder, baking soda, and flour.Stir in remaining chocolate chips.

2) Pour the batter into baking dish.Use a knife or spatula to swirl the Dulce de Leche creating a marbled effect.

3) Bake for 35 to 45 minutes. The brownies center will be slightly firm when they are done.

4) Remove from the oven and allow cool completely.