Line 2 8 inch pie pans (if using a large pie pan, only use 1) with parchment paper, spray with cooking oil or grease with coconut oil, and dust with cocoa powder. Set aside.
In a large bowl, mix together the dairy free milk and vinegar, this is our "buttermilk". Place in fridge.
In a very large bowl, whisk together the coconut flour, arrowroot flour, salt, cinnamon, baking powder, and baking soda. Set aside.
Bring the ½ C of water to a boil in a small saucepan. When it reaches a boil remove from heat and stir in the cocoa powder and coconut oil until smooth and melted.
Get the buttermilk out of the fridge and stir in the eggs, honey, and vanilla.
Stir the cocoa mixture into the dry ingredients first to cool, then the egg mixture. Beat until smooth and there are no more lumps.. Batter will be thin.
Pour the batter evenly between the 2 prepared pans. Bake 28 - 35 minutes or until center of cake springs back to the touch. Note- I'm not sure if my oven is accurate. Many readers have commented they had to bake the cakes for longer. One commenter even said hers was perfect after 60 minutes!
Cool Completely.
Frosting:
Place cocoa powder in a small bowl.
Bring the water to a boil and pour over the cocoa powder, stirring until smooth. Set aside.
Place the chocolate chips in a large microwaveable bowl.
Heat for 25 seconds, stir, and repeat until chocolate is smooth and melted. DO NOT heat for longer (trust me!) or your chocolate will turn hard and be ruined! Set aside.
Beat the butter and maple syrup until light and fluffy, about 5 minutes. Add the cooled cocoa mixture (which is VERY thick), melted chocolate, and vanilla. Mix well.
If batter is too thin, transfer to the microwaveable bowl used to melt the chocolate chips and place in fridge until just stiff enough to spread as it thickens. Frosting thickens and hardens after frosting, 10 - 20 minutes
**If you put it in the fridge too long and it hardens, place it in the microwave on DEFROST until just soft enough to mix and beat with a hand held mixer, this method still hardens but not quite as much.**
Notes
The frosting I used is similar to a ganache and slightly hardens. However, I have a link to a Paleo Buttercream Chocolate Frosting above that is soft and creamy if you prefer to use that frosting instead.
For grain free baking powder combine 1 part baking soda to 2 parts cream of tartar and 2 parts arrowroot, tapioca, or potato flour.
A word of caution: Not all coconut flour is the same - some brands are much more absorbant than others! I only recommend Bob's Red Mill or Arrowhead Mills as others may not be as absorbent and result in a wet cake.