Walnut Brownies Option: Fold in ½ cup chopped walnuts with the chocolate chips.
Coconut Oil Option: Coconut oil used for the oil will add a little richness and a little more fudginess. I recommend using refined coconut oil if you don't want any hints of coconut in the flavor. Also, melt the coconut oil, then measure, and make sure your eggs are at room temperature before using. Any cold ingredients will cause the coconut oil to "bead up" (create little solid bits in the liquid oi).
Double Batch: Double all ingredients, use a 9x13-inch baking pan, and follow the directions as is. The baking time will be similar, but you might need a few more minutes.