Birthday

Groovy Chocolate Sheet Cake

by:
January 23, 2020
4
22 Ratings
Groovy Chocolate Sheet Cake
Photo by Julia Gartland Prop Stylist: Amanda Widis Food Stylist: Anna Billingskog.
  • Prep time 15 minutes
  • Cook time 45 minutes
  • Makes One 13- x 9-inch cake
Author Notes

This Texas sheet cake is classic comfort food, with a rich cake and luscious frosting. It dates back to the 1970s, when they called things “groovy” almost as much as we use the word “fire” today. —Megan Giller

What You'll Need
Ingredients
  • For the cake:
  • 4 ounces unsweetened chocolate
  • 1/2 cup unsalted butter (1 stick), plus 1 tablespoon for greasing the pan
  • 2 cups sifted flour
  • 2 cups granulated sugar
  • 1/4 teaspoon salt
  • 1 cup sour cream
  • 1 teaspoon vanilla extract
  • 1 1/2 teaspoons baking soda
  • 2 eggs, beaten
  • For the frosting:
  • 4 ounces unsweetened chocolate
  • 7 tablespoons whole milk
  • 3 cups powdered sugar
  • 1 pinch salt
  • 1 teaspoon rum extract (you can also use vanilla extract)
  • 1/3 stick of unsalted butter, melted
Directions
  1. For the cake:
  2. Heat the oven to 350°F and grease a 13- x 9- x 2-inch pan with 1 tablespoon of butter.
  3. Melt the chocolate over a double boiler.
  4. In a separate saucepan, melt the 1/2 cup butter over medium heat along with 1 cup of hot water and bring to a low boil. Mix in the melted chocolate and stir to combine. Take off the heat.
  5. In a medium-size bowl, combine the sifted flour, sugar, and salt.
  6. Pour the chocolate mixture into the bowl with the flour mixture and combine well with a wooden spoon. Add the sour cream, vanilla, and baking soda to the mixture and combine well. Add the beaten eggs and mix until they’re fully incorporated.
  7. Add the batter to the greased cake pan and bake for 30 minutes, or until you can insert a toothpick or knife into the center and it comes out clean. Let cool completely before frosting.
  1. For the frosting:
  2. Melt the chocolate in a double boiler.
  3. In a medium-size bowl, mix the milk and sugar gradually .
  4. Add the salt and rum extract to the milk-sugar mixture and stir until combined. Then add the melted chocolate and stir until combined.
  5. Add the melted butter and mix until fully incorporated.
  6. Let the frosting cool slightly, before spreading on cooled cake.
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34 Reviews

nsfech
nsfech November 17, 2023
I love this cake! It reminds me of the Sarah Lee chocolate cake that my mom always had in the freezer for the days she didn’t feel like baking a home made dessert. I have made this countless times and it is always a huge hit. I was wondering if anyone has tried freezing the cake? Does the frosting freeze well or should I freeze the cake unfrosted?
 
sharonspens
sharonspens February 25, 2023
I am a sucker for a good chocolate cake, and the reviews of this one made it irresistible. I baked it this afternoon, with the only change being vanilla extract vs. rum extract. It is delicious, as promised - tender, and a distinct undertone with the bittersweet frosting. The cake itself has a wonderful dark color to it. The cake did not carry as strongly a chocolate flavor as I might like; I may add either a little espresso powder or a little chocolate extract the next time (and there will be a next time). I am trying not to go back for a second slice right now, but it may be futile.
 
MVaughn
MVaughn April 10, 2021
This cake is so good! It's got a great texture and delicious chocolate flavor. The icing was hard to mix by hand so I whipped it up in the stand mixer. I didn't have rum extract so I subbed vanilla. This will definitely be made again so I'll try rum extract next time.
 
Carla L.
Carla L. September 20, 2020
I have a question. Whenever I read a cake recipe it mentions using x amount of Unsalted Butter,then a bit further in the ingredients it lists x amount of Kosher Salt( I have no idea what the difference is between Kosher and non-Kosher., but that's beside the point really). Why do we need the butter UN salted and then Add Salt? Why not use regular salted butter?
 
Isa
Isa November 3, 2020
Hi Carla,
Generally recipes are written this way to allow you to add salt to taste, and not have the salt level dictated by the butter.
Kosher salt is comprised of larger flakes than regular table or sea salt, so is less dense. You definitely don’t want to substitute 1:1 or the cake can come out way too salty... With this cake I generally add a healthy pinch of sea salt to the batter and lightly sprinkle the frosting with fleur de sel before serving.
We all love this cake (though we use about half the sugar or it is too sweet!).
 
Carla L.
Carla L. November 3, 2020
Thanks for that. That does explain it!
 
marilyn
marilyn February 13, 2023
Thanks for the comment on the sugar - it does look *very* sweet.
 
Mary L.
Mary L. July 14, 2020
This cake is super sweet. I had to give it away. My friends kids loved it.
 
Alicia M.
Alicia M. February 25, 2020
So I have made this cake twice, the first time I thought maybe I did something wrong because I kept getting distracted, but this time I made sure I did everything the way it was supposed to be done and the cake turned out the same way. Now I'm wondering if that's just how the cake is supposed to be? Both times, the edges started to cook quicker than the center and I had to turn the temp down to 325 and bake the cake for an hour. Also, the cake is almost fudgy instead of cake like. Has anyone else had any of these problems?
 
Jo C.
Jo C. February 22, 2020
Sorry I am guilty of not reading your blog thoroughly. I found the answer to my question.
 
Jo C.
Jo C. February 22, 2020
On the recipe ingredients list there is no mention of water. But in the steps there is. So is the water just used for the double boiler and not included in the recipe?
 
Donald
Donald February 22, 2020
It's still annoying when water isn't listed in the ingredient list of recipes when a specific amount is required. It should be there so the preparer can assemble their mise en place.
 
Connie B.
Connie B. February 21, 2020
The story that accompanied this recipe included the fact that these ingredients can easily be cut in half to make an 8x8 cake. Good news!
 
Smaug
Smaug February 27, 2020
You could also use a 9" round pan for a half recipe.
 
Patrick
Patrick March 27, 2020
I missed this. Where does it say that? Thanks.


 
Smaug
Smaug March 27, 2020
The 8x8 was in the comments on the story. The 9' was right here- a 9" round pan has an area of 63.6 sq.in., an 8x8 is 64 sq.in. (assuming these are the actual sizes of the pans- sometimes manufacturers give nominal sizes to the pan that are not accurate)
 
calla L.
calla L. February 21, 2020
This is finger licking good. Thank you for the recipe
 
RTUCHOL2
RTUCHOL2 February 18, 2020
7 Tablespoons of milk was nowhere near enough to make this a workable icing. I had closer to half a cup of milk to make it smooth/creamy and spreadable over a cake. Might want to fix the recipe. Otherwise, a good classic chocolate cake. I personally prefer the vanilla extract over the rum. I used rum and it was just a bit odd to me.
 
LMS
LMS February 21, 2020
Since 1/2 c is 8 tablespoons, And you used “close”to that it sounds like 7 tablespoons is right on the money.
 
alison P.
alison P. February 21, 2020
1/2 cup = 8 tbs, so the recipe is just about right, according to your post.
 
RTUCHOL2
RTUCHOL2 February 22, 2020
Correction: In addition to the 7 Tablespoons listed in the recipe, I added approximately 1/2 of milk to make the frosting usable. The frosting recipe is flawed. The cake recipe is fine, and tasted similar to that of the recipe on the back of the Hershey’s cocoa box.
 
RTUCHOL2
RTUCHOL2 February 22, 2020
Correction: In addition to the 7 Tablespoons listed in the recipe.
 
Molly M.
Molly M. February 2, 2020
salted or unsalted butter?
 
Guilherme M.
Guilherme M. February 13, 2020
Unsalted ;-)
 
Donald
Donald February 22, 2020
A reasonable question. I don't ever remember seeing unsalted butter while growing up and cooking in the 1970's, the era of this cake. So I'm sure the recipe was originally created with salted butter since that's what was in every supermarket. Whether it was modified since then to use unsalted butter and add a measured amount of salt only the author could tell us.
 
Molly M.
Molly M. February 22, 2020
Thank you for updating the recipe online to answer my question. Much appreciated!
 
alison P.
alison P. February 22, 2020
i first tasted unsalted butter at my grandparents' in nyc in the 60's, so it was available some places.
 
Donald
Donald February 22, 2020
Sure it was around I'm sure, but it wasn't common and recipes sure didn't specify. I remember tasting it on a baguette in a fancy French restaurant in Chicago around 1979 and being amazed!
 
Megan
Megan January 26, 2020
Nice moist everyday chocolate cake, like the kind you dont need an occasion to make. I was lazy and skipped the double boiler and instead put butter and water and chopped chocolate in a microwave safe bowl and heated it on high for 1 minute 20 sec. I added this into the dry ingredients and followed the recipe as written. I also combined the butter and chocolate and microwaved at half power for 1 minute when I made the icing. All worked out great and lots less dishes!
 
creid
creid February 1, 2020
What kind of flour did you use? All-purpose or cake flour?
 
Megan
Megan February 1, 2020
I used AP flour.
 
creid
creid February 1, 2020
Thank you so much for the reply! I'm making this for my son's birthday tomorrow and wanted it to turn out well.
 
creid
creid February 7, 2020
Using your tips, the cake was fabulous. Thank you!
 
Allison W.
Allison W. July 5, 2020
Thank you for bringing this recipe into the modern era. I got rid of my double boiler on my last move, 20 years ago. Ridiculous that microwave instructions were not at least added as an alternative.