Preheat the oven to 350°F. Melt the butter in a 9x13-in. baking dish by placing it in the preheating oven. Once melted, remove from the oven and set aside.
Meanwhile, in a medium bowl, whisk together the flour, sugar, baking soda, salt, and cocoa powder.
Stir in the vanilla and buttermilk until a smooth batter forms. Optional: Then, fold in the chocolate chips.
Pour the batter evenly over the melted butter in the baking dish. Do not stir.
In a small bowl, combine the granulated sugar, brown sugar, and cocoa powder. Sprinkle evenly over the top of the batter.
Heat the water until just boiling, then remove from heat. Slowly pour the hot water over the entire dish. Again, do not stir.
Bake the chocolate cobbler for 35–40 minutes, or until the top looks cracked and set but the bottom is still gooey and bubbling. The centre should jiggle slightly.
Let the cool for 10–15 minutes before serving. It will thicken slightly as it sits. Once ready, serve warm with ice cream or whipped cream. Enjoy!