How long to bake a 12×18 sheet cake

My easy chocolate sheet cake is basically perfect. So fluffy and FULL of chocolate flavor, without being oily and sad like so many store bought cakes. A nice dollop of fudge transforms this buttercream into something almost magical but if you don’t have any handy try adding in some ganache!

What You’ll Need for this Recipe

For the Buttercream: You can either make a simple ganache by melting chocolate and cream, or you can use a nice runny fudge. In the recipe video I used fudge but have heard from many of you that finding the right type of fudge can be a bit tricky so if in doubt just make a ganache!

Buttermilk: I love using buttermilk in cakes but it’s not something you always have on hand so feel free to either use some buttermilk powder OR sour some milk with lemon juice or white vinegar. About a tablespoon or either mixed into a cup or milk will do the trick.

How to make Chocolate Sheet Cake

1. Preheat the oven to 350F and line a 9×12 cake pan with parchment paper. Sift the flour, baking soda, baking powder, salt, sugar and cocoa powder together into a large bowl then whisk to combine.

2. In a medium bowl add the sour cream, buttermilk, eggs, vegetable oil, and vanilla. Whisk together then mix in the hot coffee.

3. Pour the wet ingredients in with the dry and whisk to combine. Mix on low for about a minute and scrape the bowl down.

4. Transfer batter into your prepared pan and bake for about 50 minutes or until a toothpick inserted in the center comes out clean. Allow to cool for a few minutes then invert onto a wire rack and peel parchment paper off.

5. For the frosting; cream the butter in a stand mixer, add the salt and cocoa powder then mix on low until combined. Scrape the bowl down then beat in the confectioners sugar. Once your mixture has come together you can scrape the bowl down and add the fudge or cooled ganache. Mix until silky and smooth. If things are a bit stiff you can add milk or cream a tablespoon at a time until desired consistency is reached.

6. Time for the assembly! Add the buttercream to the top of the cake with an ice cream scooper. Spread and smooth with an offset spatula. You can decorate the cake with sprinkles, chopped toasted nuts or shaved chocolate. Enjoy!

There’s something so comforting about a sheet cake. It is totally low stress baking that delivers all the taste!

Pro Tips for This Recipe

• Use whole milk with a tablespoon of vinegar or lemon juice as a substitute for the buttermilk.
• Measure your flour correctly! Adding too much flour to the recipe is the most common mistake. The best, and easiest way to measure flour is by using a scale. If you don’t have one then fluff your flour with a spoon, sprinkle it into your measuring cup, and use a knife to level it off.
• You can substitute whole milk yogurt for the sour cream if desired, I do it all the time and can’t really tell the difference.
• Hate coffee? Just use warm water instead!
• If You Don’t Have Fudge Handy just whip up a quick ganache. Scald 1/4 cup of cream or milk and pour over an equal amount or semi or bittersweet chocolate chips (or chopped). Let it sit for a few minutes then whisk together. You can add more or less of this into the buttercream It’s really up to you!

Frequently Asked Questions

How many does this serve?

A 9″ x 13″ pan will yield about 30 2″x2″ pieces.

An 18” x 26″ pan will yield about 78 2″x2″ pieces.

Can you freeze it?

You can freeze a sheet cake for the ultimate make ahead treat. For best results freeze the cake unwrapped then once frozen, wrap well and store for up to 3 months. You may also want to freeze the cake and frosting separately. This way the moisture in the buttercream will not seep into the cake.

What’s the difference between sheet cake and regular cake?

Sheet cakes are one layer of, usually rectangular, cake topped with buttercream. Layer cakes are two or more layers with frosting in between. Layer cakes are quicker to assemble and can feed large groups.

If you’ve tried this chocolate sheet cake then don’t forget to leave a rating and let me know how you got on in the comments below, I love hearing from you!

Top 5 how long to bake a 12×18 sheet cake edited by Family Cuisine