For the Cream Cheese Filling:
Place cream cheese, 1 egg, 1/4 cup maple syrup, 1 tsp vanilla extract and 1/2 tsp salt into blender or medium sized mixing bowl. Blend on low speed, or use hand beaters to combine until thoroughly mixed and creamy, about 25 seconds. Set aside until above recipe calls for filling.
To make the chocolate cake:
Preheat oven to 325°F. Grease a 7-inch or 9-inch leak-proof cheesecake pan or use any shape pan your prefer (a 9“ by 13” casserole dish, a traditional 9" round cake pan lined with parchment etc.); but a leak-proof cheesecake pan is best for presentation. (If you use the 7-inch, you'll have batter left over, with which I make 2-3 black bottom cupcakes!)
In a medium sized bowl, sift together the dry ingredients: 3/4 cup cocoa powder, cassava flour, baking soda and 1/2 tsp sea salt. Set aside.
In a large bowl, using a hand mixer, blend together oil, water, 3 eggs and 2 tsp vanilla. Alternatively, combine them in a blender or briskly by hand.
Add the dry ingredients to the wet ingredients and fold together with a rubber spatula until completely combined. Do not over-mix. Pour into the greased pan.
Using 2/3 of the mixture, ladle large dollops of the cheese filling around the surface of the cake. Use a spoon to push down 1-2 inches on each dollop, so the filling goes into the center of the chocolate batter. Use a spatula to scrape the remaining cheese batter over the surface of the cake; and spread it out evenly, not all the way to the edges, leaving about 1/2 an inch of chocolate batter showing around the circumference of the pan.
Bake for about 45 minutes in preheated oven until the edges are puffed and the center is slightly puffed and golden and beginning to look dried out on the top with very little jiggle if you shake the pan side to side. Cooking times will vary slightly based on the size of the pan and the depth of the cake; check cake(s) after 25 minutes if you're using the batter divided between two pans (see Recipes Notes for this idea).
Allow to cool. Using a wooden knife, unclasp the outer ring of the pan and slide the knife around its circumference. Remove pan's sides. Use wooden knife again, if needed, to release the base of the cake from the pan base. Transfer cake to serving plate. Sift remaining cocoa over its surface until cream cheese is completely or partially covered, whatever looks prettiest to you. Refrigerate until ready to serve.