Step 1: Pour melted butter into slow cooker.
Step 2: In a medium-sized mixing bowl, combine the flour, baking powder, salt, sugar, cocoa, melted butter and milk until smooth. Pour into the slow cooker over the melted butter.
Step 3: In a small bowl, combine the sugar, brown sugar, cocoa powder and salt. Sprinkle over the batter; do not stir.
Step 4: Pour the boiling water on top of the rest; again, do NOT stir.
Cook on high for 2 hours or low for 3-4 hours. Once the cobbler is done, there will be a light and fluffy chocolate cake on top and a rich chocolate sauce on the bottom. Serve with whipped topping and/or ice cream, if desired.