Preheat oven to 350 degrees F (176 C) and butter three 8" round cake pans (or line 24 muffin tins with paper liners // adjust number/size of pans if altering batch size). Dust pans with gluten free flour and shake out excess.
Measure out almond milk in a liquid measuring cup and add vinegar. Stir and let curdle while moving onto the next step.
Prepare flax eggs by mixing water with flaxseed meal in a large mixing bowl and let rest for 5 minutes.
Next, add baking soda to the almond milk vinegar mixture and stir. Set aside.
Add the oil, cane sugar, and maple syrup to the flax egg and beat/whisk to combine.
Next, add applesauce, vanilla, and salt and beat/whisk to combine. Then add almond milk mixture and whisk again.
Lastly, add baking powder, cocoa powder, almond meal, oat flour, and gluten-free flour and beat/whisk to combine, making sure no large clumps remain.
If the batter appears too thick, add a touch more almond milk, but it should be perfect. It should resemble a semi-thick batter that’s pourable.
Divide batter evenly between the three prepared cake pans (or muffin tins). Bake cakes for 30-40 minutes (cupcakes for about 28-35 minutes) or until a toothpick inserted into the center comes out completely clean and the edges appears dry. (Time will vary if you subbed ingredients, as well as depending on the size of your pans.)
Let cake rest in the pans for 15 minutes, then carefully run a butter knife along the edges and invert onto cooling racks. Let cool completely.
In the meantime, prepare your coconut whipped cream. Follow these instructions to make a double batch, sweetened to taste (I found 6-8 Tbsp | 42-56 g to be the right amount // amount as original recipe is written // adjust if altering batch size). Set in the refrigerator to chill/firm up while cake cools completely.
NOTE: Assemble just before serving so the whipped cream doesn’t over-moisten the cake.
To assemble, lay down one cake bottom side up on a serving plate or cake stand. Spread on a semi-thick layer of coconut whipped cream and top with second cake, also bottom side up. Frost with another layer of coconut whipped cream.
Carefully top with remaining cake (also bottom side up) and frost the top generously with remaining coconut whipped cream. (You may not use it all, which you can reserve for serving). Top with berries and serve immediately (or cover and chill in the refrigerator until serving).
Leftovers will keep covered with a cake stand or plastic wrap in the refrigerator for 2-3 days, though best when fresh. (The unfrosted cake will keep covered at room temperature for several days.)
*For the gluten-free flour blend, I've tested both with my DIY Blend and Bob's Red Mill Gluten Free 1:1 Baking Blend and found that I slightly preferred the Bob's blend in terms of the cake's texture. However, both will do! *Nutrition information is a rough estimate calculated with generous amounts of coconut whipped cream and berries (calculated using coconut cream, not coconut milk). *Prep time does not include chilling coconut cream or cooling cake. *Adapted from my 1-Bowl Chocolate Hazelnut Cake.