Lightly spray slow cooker with nonstick cooking spray.
In a mixing bowl whisk together dry cake ingredients. Add coconut milk, vanilla, and melted butter, and stir just until combined. Spread cake batter in a 3-4 quart slow cooker. Batter will be thick. Sprinkle chocolate chips over the batter.
Whisk together sauce ingredients and pour over the top of cake batter (do not mix in with the cake batter). Cover and cook on high 2-3 hours, or until the top is set. Turn off slow cooker and allow cake to set covered for 15 minutes before serving.
Notes
Hot Fudge sauce will be on the bottom of the cake.