Preheat oven to 350 degrees F. Place walnut halves on a baking sheet. Toast walnuts in oven for 8-10 minutes or until fragrant and slightly toasted. Allow walnuts to cool on baking sheet for 5 minutes.
Pour brownie batter to a 10-inch skillet coated with nonstick cooking spray or to 9x9 inch square baking pan. Sprinkle walnuts on top. Bake for 23-27 minutes or until brownies are done and a tester comes out clean or with just a few crumbs attached.
To make vegan: I think you could easily make this vegan by using a flax egg.
To reduce sugar in the recipe: Leave out chocolate chips from the batter and just use the drizzle -- or leave off both. I promise they'll still be delicious!