Prepare the Chocolate Base. In a mixing bowl, combine the all-purpose flour, cocoa powder, sugar, baking powder, and a pinch of salt. Add milk, melted butter, and vanilla extract. Stir until a smooth batter forms.
Create the Topping. In a separate bowl, mix sugar, quick oats, and cocoa powder. Sprinkle this mixture evenly over the chocolate batter.
Add the Brown Sugar Layer. Sprinkle brown sugar over the cocoa-sugar topping. This layer will melt into a gooey, caramel-like sauce during baking.
Pour Boiling Water. Gently pour boiling water over the entire concoction. This seemingly unusual step is the secret to creating a rich, saucy layer beneath the crumbly topping.
Bake to Perfection. Place the dish in the preheated oven and bake until the cobbler is set, and the top forms a beautiful, crusted layer.
Serve and Savor. Scoop out portions of warm cobbler, ensuring each serving has a bit of that gooey chocolate sauce. Pair it with a scoop of vanilla ice cream for an extra indulgence.