Spread each of the brownies with 1 tablespoon of nutella. Sprinkle each of the brownies with 1 tablespoon chopped hazelnuts. Top the nuts with 1 tablespoon mini chocolate chips. Place the brownies on a baking sheet and bake for 5 to 7 minutes until the chocolate is starting to melt. Transfer the brownies to the refrigerator and let cool until the chocolate hardens, about one hour.