The cake is a one-bowl melted-butter batter with cocoa and buttermilk, baked in a 9-by-13-inch pan for 25 to 30 minutes.
Four cups of mini marshmallows go over the hot cake for two minutes to soften, then a warm cocoa frosting with a cup of chopped pecans is poured over the top. Contains tree nuts.
Why This Recipe Works
- Melted butter gives a dense, fudgy cake crumb.
- Two minutes in the oven softens the marshmallows without melting them flat.
- Pouring the frosting warm lets it settle over the marshmallow layer in a smooth sheet.
- Buttermilk keeps the crumb tender under the heavy topping.
Three Layers in the Pan
Built in order, each while the one below is still warm.
Pecan cocoa frosting
Butter, cocoa and milk simmered, then powdered sugar, vanilla and pecans.
Marshmallow
Four cups of mini marshmallows, back in the oven for 2 minutes.
Chocolate cake
Baked 25 to 30 minutes until a tester has a few moist crumbs.
How to Make It
Pan greased
Heat oven to 350°F. Grease a 9-by-13-inch baking pan.
Batter mixed
Whisk the melted butter with granulated sugar, eggs and 1 teaspoon vanilla. Fold in flour, 1/2 cup cocoa and salt, then stir in buttermilk until smooth. Spread in the pan.
Baked and marshmallowed
Bake 25 to 30 minutes, until a toothpick inserted in the cake layer comes out with a few moist crumbs. Scatter the mini marshmallows evenly over the hot cake and return to the oven for 2 minutes, just until puffed and softened.
Frosting cooked
For the frosting, melt the remaining 1/2 cup butter in a saucepan. Whisk in 1/3 cup cocoa and milk, bring just to a simmer, then remove from heat. Whisk in powdered sugar and 1 teaspoon vanilla until glossy; fold in chopped pecans.
Poured and cooled
Pour the warm frosting over the softened marshmallow layer. Cool completely before cutting into 15 squares.
Ingredient Notes
- Mini marshmallows
- Four cups, scattered over the cake while it is still hot.
- Pecans
- One cup, chopped and folded into the warm frosting.
- Cocoa powder
- Half a cup in the cake and a third of a cup in the frosting.
Success Tips
- Scatter the marshmallows right out of the oven so they soften evenly.
- Pour the frosting in a steady stream from the middle outward.
- Cool completely before cutting so the layers stay separate.
Serving Ideas
Cut into fifteen squares and serve from the pan, marshmallow layer visible in each slice.
Storage and Reheating
Refrigerate
Cover and keep at cool room temperature up to 2 days or refrigerate up to 5 days.
Frequently Asked Questions
Does it contain nuts?
Yes, a cup of chopped pecans in the frosting.
How does the marshmallow layer stay separate?
It softens for only two minutes, then the warm frosting is poured over it.
