Nana Lou called this her last-minute chocolate fix—three pantry staples, one pan, and everyone hovering by the oven.

For picky eaters who like things extra sweet and simple, use a milk chocolate cake mix instead of dark or devil’s food so the flavor is a little softer. If your crew loves extra chocolate, sprinkle 1/2–1 cup of chocolate chips over the sweetened condensed milk before adding the dry cake mix. For a slight mocha twist, stir 1–2 teaspoons of instant coffee granules into the dry cake mix before sprinkling it over the pan. You can also use salted butter if that’s what you keep on hand; the tiny hint of salt makes the chocolate flavor pop. If you want smaller portions for little ones, bake the mixture in two 8×8-inch glass dishes instead of one big one and shorten the bake time by a few minutes. For make-ahead ease, you can assemble the dry mix and melted butter layers, then cover and refrigerate the unbaked pan for a few hours; let it sit on the counter while the oven heats, then bake as directed. Serve it plain for kids who don’t like toppings, and set out bowls of ice cream, whipped cream, or berries on the side so everyone can build their own bowl the way they like it.