Preheat oven to 350° F. Grease and flour a 9x13-inch pan.
In a medium mixing bowl, whisk the gluten free flour blend, cocoa powder, and baking soda until combined.
In a large mixing bowl, whisk the oil, sugar, egg, and vanilla until combined.
Stir the dry ingredients into the wet ingredients until combined. (Note: The mixture will be dry and crumbly.)
Add the zucchini and stir until well combined.
Transfer the batter to the prepared pan. Use a rubber spatula to spread the batter evenly around the pan.
Bake for 25-30 minutes until a wooden pick, inserted in the center, comes out with a few moist crumbs.
Make the Frosting:
While the brownies are cooling, combine chocolate chips, almond milk, butter, and vanilla in a microwave-safe bowl. Microwave on high for 35-45 seconds.
Remove from microwave and whisk until chocolate chips are completely melted and the mixture is smooth. Microwave for a few more seconds if necessary.
Whisk in the powdered sugar until smooth.
Spread the warm frosting over the top of the brownies.
Allow the frosted brownies to cool completely before slicing and serving.
Notes
Check the ingredients of your gluten free flour blend for xanthan gum. If your flour mix doesn’t contain xanthan gum, try adding ½ teaspoon to the recipe.
Use a room temperature egg. An egg at room temperature will mix more easily into the batter.
The zucchini should be grated but not drained. Many baking recipes call for squeezing the excess water out of the zucchini, but in this case the water adds moisture to the brownies.
Allow the frosted brownies to cool completely before serving. It’s easier to cleanly cut brownies that have cooled completely.