Make the Cupcakes
Melt the butter in a saucepan over moderate heat. Whisk in the cocoa powder. Remove from the heat and let cool. Beat the 8 egg whites and cream of tartar together until stiff peaks form. Set aside.
In a separate bowl, mix together 2 whole eggs, 8 egg yolks, coconut milk, sugar, salt and vanilla. Stir in the cocoa-butter mixture. Whisk the coconut flour into the batter until there are no lumps. Fold the egg whites into the batter.
Divide the batter equally between lined muffin cups and bake for 20 minutes, or until a toothpick inserted in the center comes out clean. Transfer baking tin to a wire rack and let the cupcakes cool for 10 minutes. Carefully remove the cupcakes from the tin and place on the wire rack to cool completely.
Meanwhile, Make the FrostingsCoconut-Pecan Frosting: In a medium saucepan, whisk together the coconut milk, cornstarch, sugar, egg yolks and butter. Cook over medium heat, stirring constantly until the mixture thickens. Remove from the heat and add the vanilla, coconut and pecans. Let cool before frosting the cupcakes.
Chocolate Buttercream Frosting: Put the chocolate in the top pan of a double boiler set over simmering water. Stir until the chocolate is melted and smooth. Set aside and let cool to room temperature.
In a large mixing bowl or stand mixer, beat together the sugar, butter, milk, vanilla and salt until light and fluffy, about 2 minutes. Add the chocolate and beat for one more minute.
Place one tablespoon of the coconut pecan frosting on the top of each cupcake. Pipe the chocolate buttercream frosting up and around the coconut pecan frosting. Serve or store in an airtight container for up to two days.