Make chocolate cakes by measuring out almond milk in a liquid measuring cup, adding apple cider vinegar (or lemon juice) and baking soda, and stirring. Set aside.
In a large mixing bowl, prepare flax eggs by combining water and flaxseed meal. Let rest for 5 minutes while you prepare your other ingredients.
Add the oil, coconut sugar, and maple syrup and whisk to combine.
Next, add applesauce, vanilla, and salt and whisk to combine. Then add almond milk mixture and whisk again until everything is thoroughly incorporated - about 30 seconds.
Lastly, add baking powder, cocoa powder, almond meal, oat flour, and gluten-free flour, and whisk to combine, making sure no large lumps remain.
Transfer batter to the refrigerator to chill/thicken for 20 minutes, and preheat oven to 350 degrees F (176 C). Grease two large baking sheets (use more or less if altering batch size) with nonstick spray (if you don’t have two baking sheets, just use one and bake the cakes in 3-4 batches).
Once the oven is preheated, scoop out 1 heaping Tbsp amount of batter onto the prepared baking sheets, leaving at least 1-inch of room for spreading. Use your tablespoon to slightly spread them into a small disc. One standard baking sheet should fit 12 cakes. Repeat on second baking sheet.
Bake for 10-14 minutes, or until the edges appear dry. (I found 12 minutes to be the perfect time.) Remove from oven and let rest on baking sheet for 5 minutes, then carefully transfer to cooling racks to cool completely.
Repeat this process, baking the mini cakes until all batter is used - you should have about 40-48 total cakes.
Once the cakes are completely cooled, arrange half of the cakes on 1-2 baking sheets (upside down) and top each with a chocolate square and several halved marshmallows.
Broil on the top rack of the oven on high broil until toasty and brown. Watch carefully as they will burn/toast quickly! (Alternatively, if using a grill or campfire, toast the marshmallows over the fire and place between cakes once toasted).
Top with fruit (optional) and another cake of similar size and shape and press down slightly.
Enjoy immediately! Best when fresh.
Leftover cakes will keep covered at room temperature up to 3 days or in the freezer up to 1 month.
*Whoopie Pie Cakes from my Vegan Whoopie Pies. *Nutrition information is a rough estimate calculated with chocolate and fruit.