This easy chocolate pudding cake bakes into a soft, brownie-like chocolate cake with a warm, fudgy chocolate sauce underneath. The hot cocoa-coffee topping goes over the batter without stirring, then the cake and sauce form into separate layers as it bakes.
Prepare the oven and baking dish: Preheat the oven to 350°F. Butter a 10.5 x 7.5-inch ceramic baking dish well.
Mix the dry ingredients: Whisk the flour, granulated sugar, brown sugar, cocoa powder, baking powder, and salt together in a medium bowl.
Make the batter: Add the milk, melted butter, and vanilla extract. Stir with a spatula just until smooth. The batter will be thick, similar to a stiff brownie batter.
Add the chocolate chips: Fold the chocolate chips into the batter.
Spread the batter: Transfer the batter to the prepared baking dish and spread it into an even layer, working it into the corners. The layer will look relatively thin, but it will rise considerably as it bakes.
Make the pudding topping: Whisk the light brown sugar, granulated sugar, cocoa powder, and salt together in a small bowl. Slowly pour in the hot coffee or boiling water while stirring. Continue stirring until mostly smooth, pressing any remaining cocoa lumps against the side of the bowl with the back of a spoon.
Pour over the batter: Slowly pour the hot pudding mixture evenly over the batter. Do not stir.
Bake: Bake for 30 to 35 minutes, or until the top is set and slightly cracked and springs back lightly when touched. The sauce should be bubbling around the edges, and the center may still have a slight jiggle from the sauce underneath.
Let it rest: Let the pudding cake rest for 15 minutes before serving. The chocolate sauce will thicken into a fudgier consistency as it sits.
Serve: Scoop into bowls, digging all the way to the bottom so each serving gets both cake and chocolate sauce. Serve warm with vanilla ice cream or lightly whipped cream and flaky sea salt, if desired.
Notes
Add the hot liquid slowly: Pour the hot coffee or boiling water into the cocoa-sugar mixture gradually while stirring to help prevent cocoa lumps. Press any remaining lumps against the side of the bowl with the back of a spoon.
Do not stir after pouring: Once the hot pudding mixture is poured over the batter, leave the layers separate so the cake can rise while the chocolate sauce forms underneath.
Do not overbake: Look for a set, slightly cracked top with sauce bubbling around the edges. A slight jiggle from underneath is fine. Overbaking can cause the cake to absorb too much of the sauce.
Let it rest: The sauce will be thinner straight from the oven. Rest the cake for 15 minutes so it can thicken while remaining warm and spoonable.