- 1 chocolate cake mix, plus the ingredients indicated on the box
- 2 sticks unsalted butter, room temperature
- 1 7oz jar of marshmallow creme
- 1 tsp pure vanilla extract
- 1/2 tsp salt
- 2 level cups of powdered sugar
- 1 TBS milk
- 12-13 whole graham cracker sheets
- 2/3 cup chocolate chips
- 2 cups (approximate) mini marshmallows
- Lightly grease a deep (3-inch is best) light metal 9x13 pan and set aside.
- Line the center rack of oven with aluminum foil to catch any overflow and pre-heat to 350F.
- In a mixing bowl, prepare cake mix batter as indicated on the box. Set aside.
- Using a hand or stand mixer, combine the butter, marshmallow creme, vanilla extract, and salt until fluffy. With mixer on low, add the powdered sugar in several additions and mix until starting to incorporate, and then add the milk and increase mixer speed and mix well until fully combined, smooth, and fluffy.
- Spread a thin layer of the chocolate cake batter in the bottom of the prepared baking pan and arrange 9-10 of the whole graham cracker sheets on top of the batter in a single layer.
- Pour a bit more of the cake batter over the graham crackers until totally covered and sprinkle on the chocolate chips.
- Top with the rest of the cake batter and smooth with a rubber non-stick spatula.
- Dollop the marshmallow frosting on top of the cake batter and gently swirl it into the batter, being sure not to disturb the layer of graham crackers on the bottom.
- Bake according to cake mix instructions (usually 25-35 minutes). PLEASE NOTE: As the frosting settles into the batter, this may cause some overflow of the batter out of the pan, especially in shorter 9x13 pans. This is typical of frosting-in-the-cake recipes and is the reason for the foil covering the oven rack. If you want, keep a few folded paper towels or a spoon nearby and if you notice some overflow you can open the oven and quickly wipe it away as it happens.
- Cake is done when mostly set and when it springs back gently when you press on the center with your fingertips. Watch your cake and adjust bake time accordingly. Toothpick test will not work, as the interior is so moist. The fully baked cake will have cracks and holes on it - this is normal!
- Remove the cake from the oven and turn the oven to Broil. Break the remaining graham cracker sheets into pieces and sprinkle them, along with the mini marshmallows, on the top of the cake. Broil until marshmallows are toasted, then remove and allow the cake to cool a bit before cutting into it. Serve warm (yum!) or at room temperature.