Preheat oven to 350°F. Grease square baking pan.
Using double boiler, melt chocolate and oil, stirring until well combined. Add sugar and stir. Allow to cool to room temperature.
Whisk in egg, followed by vanilla, salt & baking powder. With wooden spoon, stir in flour until well incorporated, then mix in zucchini and any optional additions.
Spread mixture into pan and cook 20-25 minutes until toothpick inserted in center comes out clean. Cool in pan before inverting and slicing.
Brownies are a little delicate, so be careful when removing from pan.