Preheat oven to 350°F (180°C). Place a 10" (25 cm) cast-iron skillet on the stovetop over low heat.

Add in butter and allow to melt gently without bubbling. Once melted remove from the heat.

Stir in the white and brown sugar.

Next, crack in the eggs and add the vanilla. Using a fork, whisk these ingredients together. Note: make sure the pan isn't HOT when you add in the eggs or it will cook them.

Stir in flour, cocoa powder, and salt and mix until you have a smooth brownie batter. Don't beat as it will toughen your brownies.

Fold in the chocolate chips and walnuts.

Spread the brownie batter evenly into the skillet and finish by sprinkling over a few extra chocolate chips and chopped walnuts.

Bake for 25-30 minutes or until the brownie is JUST set to touch. Baking Note: The skillet retains heat so once you remove it from the oven the brownies will actually continue to cook so take it out of the oven when they are a little 'under' done. As the brownie cools it will set up and be perfect and fudgy.

Once cooled down slightly, top with vanilla ice-cream and dig in! Store leftovers in an airtight container at room temperature for up to 3 days.