Preheat the oven to 350°F. Grease a 9-inch square baking dish and set aside.
In a large bowl, whisk together the flour, ½ cup of the granulated sugar, ¼ cup of the cocoa powder, baking powder, and salt.
Add the milk, melted butter, and vanilla extract to the dry ingredients and mix until smooth.
Stir in the chocolate chips. This batter will be thick.
Spread the batter evenly in the prepared baking dish.
In a small bowl, whisk together the remaining ¼ cup granulated sugar and 2 tablespoons cocoa powder.
Sprinkle this mixture evenly over the batter in the baking dish.
Pour the hot water over the top of the batter and cocoa mixture. It’s important to not stir this!
Bake for 35 to 40 minutes or until the cake is set and the top is slightly cracked.
Let cool for 5 to 10 minutes before serving.
Serve warm with whipped cream or vanilla ice cream, if desired. Enjoy!