This is the way I make these—I’ve streamlined the recipe by using the microwave to melt the butter in the same bowl I use to mix up the brownies. I have no idea of the original source. A teaching colleague was eating one for lunch many years ago and it looked so good that I asked her for the recipe. My best estimate for the sugar content for one brownie, if cut into 24 bars, is 15 grams. The butterscotch chips would have a little more sugar, the chocolate chips a little less. But you'd better content yourself with just one!
Mix dry ingredients into the butter/sugar/egg mixture.
Stir in optional nuts and chips.
Spread batter into a 9x12 baking pan.
Bake at 350 for 30 minutes.
People go absolutely crazy over these, and they are the easiest brownie recipe I have. You'll note that the recipe makes a whole 9x12 panful, which is more than most brownie recipes. I've said that you'll get 24 brownies out of this, which will be true if you make them fairly small--4 across and 6 down. You can certainly make them bigger.