My kids beg me to make this every single Friday after school. I can’t believe this is only 4 ingredients.

Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with aluminum foil, letting it hang over the edges for easy lifting later. Lightly grease the foil with a bit of the melted butter or nonstick spray so the brownies release cleanly.
In a large mixing bowl, add the dry chocolate fudge cake mix (do not prepare it according to the box; use it dry). Pour in 1/4 cup of the melted butter and crack in the 2 eggs. Stir with a sturdy spoon or spatula until the mixture is thick, glossy, and evenly combined. It will be stiffer than regular cake batter—more like a very thick brownie batter.
Scrape the batter into the prepared foil-lined pan. Use the back of a spoon or an offset spatula to press and spread it into an even layer, making sure it reaches all the corners. Because the batter is thick, take your time and smooth the top as best you can so it bakes evenly.
Bake on the center rack of the preheated oven for 18–22 minutes, or until the top looks set and a toothpick inserted in the center comes out with moist crumbs but not wet batter. These are meant to be fudgy, so don’t overbake. While the brownies are baking, prepare the simple frosting so it’s ready to pour over the warm base.
For the frosting, place the powdered sugar in a medium bowl. Add the remaining 1/4 cup melted butter. Pour in 2–3 tablespoons of hot water, 1 tablespoon at a time, stirring after each addition, until the frosting becomes smooth, thick, and pourable. You want it to be glossy and able to spread on its own but not runny. If it gets too thin, add a spoonful more powdered sugar; if it’s too thick, add a few more drops of hot water.
As soon as the brownies come out of the oven, set the hot pan on a heatproof surface and immediately pour the warm frosting over the hot brownie surface. Gently tilt the pan or use a spatula to help the frosting flow into an even, thick, glossy layer that covers the entire top. The warmth of the brownies will help the frosting settle into that classic lunch-lady sheen.
Let the brownies cool in the pan on a wire rack until the frosting is set and the brownies are just slightly warm, 30–45 minutes. Using the foil overhang, lift the whole slab out of the pan and place on a cutting board. Peel the foil away from the sides, then cut into 12 generous squares (or smaller pieces if you prefer). Serve warm or at room temperature, right off the foil-lined tray for that nostalgic, no-fuss cafeteria feel.
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