These are my experiments with boxed brownie mix.
The Internet research pointed me to a babycenter group (The Exclusive Pumpers) who had tried this back in 2013. One poster suggested adding 3 Tbsp flax meal and 2 Tbsp Brewers yeast straight to a boxed mix. That sounded easy. I wanted oatmeal too though so I added half a cup, that didn't seem like quite enough so I added another 1/4th cup for a total of 3/4 cup.
I pick up brownie mixes when I see them on sale and keep them for when I need a quick dessert. The first mix I had in my cupboard was Duncan Hines Dark Chocolate Brownie Mix. I hoped to find a recipe that would work with any mix.
The brownies were delicious, they tasted like fudgey brownies. They did not rise at all though, I probably could have used the 2 eggs for cakey brownies.
Here is my suggested recipe:
1 box brownie mix and ingredients listed on the box (usually eggs, water, and oil)
2 Tablespoons Brewers Yeast
3 Tablespoons Flax Meal
3\4 cup rolled oats.
1-2 Tablespoons extra water.
Mix all dry ingredients in a large bowl (brownie mix, oatmeal, flax, brewer's yeast)
Add egg(s), oil, water, per box instructions. Mix the batter together with a mixing spoon. The batter should be easy to stir but not runny, if it is too stiff then add an extra Tablespoon or two of water.
Spread into a greased pan and bake per the box instructions.
Some tips for the novice baker:
-Set you timer for the shortest time in the baking directions, check if they are done, if not close the oven for another minute or two. Repeat at the end of that minute.
-instructions usually say to insert a fork and if it comes out clean they are done. You are looking for drippy or gooey batter on the fork, that means it needs more time. A crumb or two on the fork means they are done.
-set the pan on a cooling rack or hot pad or trivit on the counter to cool. The heat from the oven will continue to cook the brownies if you set the pan on the stove.