Preheat oven to 350°F. If using springform pans, grease them, or line regular cake pans with parchment paper. Cake size options: two 9-inch cake pans, three 6-inch cake pans, or two 8-inch cake pans with parchment paper and set aside.
In a large mixing bowl, whisk together the flour, sugar, cacao, baking soda, and salt; set aside.
Scoop the avocado into the bowl of a stand mixer, and use the whisk attachment to beat until it is mostly smooth and creamy.
Add the eggs and whisk until combined. Add the maple syrup, milk, and vanilla.
Add the dry ingredients to the wet ingredients in three increments, and beat to combine, scraping down the bowl with a spatula between additions.
Pour the batter evenly into the prepared cake pans. Bake cakes for 30-35 minutes, or until a toothpick inserted in the center comes out clean. Leave the cakes in the pans for 10 minutes, then run a knife or offset spatula along the edges and carefully invert them onto a cooling rack.
Allow cakes to cool before icing.