1. Preheat the oven to 350° Fahrenheit (177° Celsius).
2. Grease two or three 8 inch round baking pans or one 9x13 inch rectangular pan. Optionally, line the bottoms with a circular sheet of parchment paper. Set aside.
3. Stir flour, sugar, cocoa powder, baking soda, salt, and optional chocolate chips in a large mixing bowl until well combined.
4. Peel avocado and discard the pit. Mash with a fork until completely smooth.
5. Gently warm almond butter or coconut oil in a saucepan or microwave until thin and very easy to stir. This will prevent clumping later.
6. Add the water, avocado, almond butter or oil, and pure vanilla extract to the bowl of dry ingredients. Stir until just evenly mixed. For best results, do not overbeat the batter.
7. Divide evenly among the prepared cake pans. Bake on the center rack of the oven for 20 minutes or until a toothpick inserted into the center of a cake comes out mostly clean.
8. Let fully cool. I recommend covering the cooled avocado chocolate cake and leaving on the counter overnight for a better texture before frosting.
9. Go around the sides of the pans with a knife and invert cakes onto large plates.
10. Frost the bottom later, then carefully place a second cake layer on top with your hands. (See the recipe video for a visual representation of this step.) Frost this layer.
11. If making a triple layer cake, repeat the process for the top layer. Garnish as desired.
12. Tightly cover any leftovers and store on the counter for one day or in the refrigerator for up to four days. Or slice and freeze in an airtight container for up to three months.