Pre-heat oven at 350 degree Fahrenheit (or 150 degree centigrade).
Grease a 9x13 baking pan with butter. Line it with parchment paper.
Pick small zucchini as they have more moisture. More moisture = moistest brownies!
Grate zucchini. Use small side of your grater so you get little shreds of zucchini. No one will be able to tell or see any zucchini in the brownies.
DO NOT DRAIN. Keep it aside until you get other ingredients prepped.
In a large bowl add all the dry ingredients – all purpose flour, cocoa powder, baking soda, and salt. Mix until well combined. Keep aside.
In another large bowl, whisk together granulated sugar, oil and vanilla extract until combined.
Now add dry ingredients in parts. Add little at a time to the wet ingredients and whisk until combined. Add the second part, continue to whisk until combined. Add the final third part and whisk until everything comes together.
Note at this point the mix will be dry and powdery, don’t worry. It will come to right consistency after zucchini is mixed in. Do not get tempted to add water or milk at this stage. Hold on to that temptation.
Add all of the grated zucchini along with all the liquids in it. Fold in gently until everything comes together.
Allow the batter to rest for 5 minutes.
The moisture in zucchini will loosen the brownie batter and bring it to right consistency. See pic.
If batter is not wet enough, let it rest for 5 more minutes.
If you like to add choco chips or choco chunks, now is the time. It makes brownies extra chocolatey.
Pour brownie batter into the baking pan. Spread it evenly. Shake the pan few time to release any bubble from the bottom of the pan.
Bake brownie in pre-heated oven at 350 degree Fahrenheit for 25 to 35 minutes.
Brownies are done with an tooth pick inserted in the center of the pan is removed with crumbs. You should not see any wet batter on the toothpick.
Remove the pan from the oven and allow it to cool completely.
Meanwhile you can get the frosting ready. In a bowl whisk together powdered sugar, cocoa powder, melted butter, vanilla extract and little water as needed.
Spread frosting evenly over cooled brownies, allow it to set completely in the fridge for couple of hours.
Once set, remove brownies from the baking pan. Using sharp knife cut into bars and serve.
These brownies will firm up once cooled and tastes even better on day two!
Keep the leftovers covered in air tight containers in fridge. You can also freeze them.