Preheat oven to 350 degrees F, and line an 8x8 baking pan with parchment paper.
Add 1 cup of chocolate chips in a bowl and microwave in 30 second increments until smooth when stirred. You can also use a double boiler. Set aside to cool.
Place avocado, eggs, sugar, and vanilla extract in a food processor, and process until smooth and creamy. Stir in melted chocolate.
1 medium avocado, 3 large eggs, 3/4 cup granulated sugar, 1 tsp vanilla extract
Stir in cocoa powder, arrowroot starch, and sea salt until combined.
1/4 cup cocoa powder, 2 tbsp arrowroot starch, 1/4 tsp sea salt
Add 1/2 cup of chocolate chips (reserve 2 tbsp if you want to sprinkle some on top of the brownies - I didn't) and zucchini, if using. Fold to combine.
OPTIONAL: 1 cup finely grated zucchini
Transfer to the prepared baking pan and spread to an even layer with a spatula. Add reserved chocolate chips on top, if using.
Bake for 30-35 minutes, until a toothpick inserted in the center comes out with a little bit of crumbs.
Remove from the oven, cool, then remove from the pan. Slice into 16 squares, sprinkle with sea salt if using, and enjoy!
OPTIONAL: flaky sea salt