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    Home » Desserts » 20 Minute Sheet Cake Brownies With Fudgy Icing

    Published: Sep 24, 2020 · Modified: Feb 26, 2022 by Nancy · This post may contain affiliate links.

    20 Minute Sheet Cake Brownies With Fudgy Icing

    Jump to Recipe Print Recipe

    Delicious 20 minute sheet cake brownies have an old fashioned bottom cake with a sweet, fudgy icing full of nuts. Makes enough to feed a crowd!

    Two brownies with nuts on top sitting on an orange plate with a fork next to it

    My neighbor Susan's 96-year-old Aunt Helen has a collection of hand written recipes that she has built over many years, and I was lucky enough to borrow them. This is one that they made frequently. Kevin took one look at the name of the recipe and said "I could be eating brownies in 20 minutes? What are we waiting for?" So I turned on the oven and mixed up a batch!

    A large index card with the hand written recipe for 20 minutes brownies on it
    Aunt Helen's original handwritten recipe for 20 Minute Sheet Cake Brownies

    What is a Jelly Roll Pan?

    20 Minute sheet cake brownies with nutty fudge frosting in a jelly roll pan
    The thin jelly roll pan makes enough to share with a crowd

    I love to make brownies, and I usually make them in an 8 x 8 pan or occasionally a 9 x 13 pan for a double recipe. But I had never made brownies in a jelly roll pan. In fact, I didn't even know what a jelly roll pan was! It is a roughly 10 x 15 sheet pan with 1" high sides that is usually used for making cake rolls. It is smaller than a half-sheet cake pan which is 12 x 18. You can use either one, but I prefer the 10 x 15 jelly roll pan because with the half-sheet cake pan the brownies (or whatever you're baking) will turn out much thinner.

    Comparing These to Modern Brownies

    What I love about these brownies is the very soft, fluffy, cake-like bottom layer that's not too sweet, topped by a firm, solid, sweet layer of icing that's almost like a thin layer of fudge. The brownies are slim which makes them a nice and light dessert or snack. Modern brownies tend to be much thicker and chewier, often with candy, caramel, nuts or chocolate chips inside. While they both have their merits, the speed, simplicity and lightness of this mid century recipe can't be beat. Modern brownies seem to taste best warm out of the oven, but these are better after they have had time to cool completely, even overnight, so that the icing has properly solidified into its fudge-like candy coating.

    Sheet Cake Brownies are Fit For a Crowd

    If you need a dessert recipe to feed a lot of people, this is the perfect one because it will yield roughly 35 2-inch square servings. My neighbor used to take these brownies to share at work. It would also be great for a picnic, potluck, or a large holiday gathering.

    You'll Need These Ingredients

    • All purpose flour
    • Sugar
    • Butter or margarine
    • Unsweetened cocoa powder
    • Milk
    • Vinegar
    • Eggs
    • Baking soda
    • Vanilla extract
    • Powdered sugar
    • Pecans or other nuts (optional)

    Tips For Perfect 20 Minute Sheet Cake Brownies

    1. Grease your pan with butter or spray it with non-stick cooking spray.
    2. Make icing while brownies are baking so it's ready as soon as they come out.
    3. Add nuts to icing immediately after mixing. Icing hardens and you won't be able to add them in later. If you don't want nuts, it's okay to skip them entirely.
    4. Apply frosting immediately after cake comes out of the oven, while it's still hot. Since this icing solidifies into a candy-like coating, it spreads and adheres best when the cake is hot.

    A Couple of Notes About the Hand Written Recipe Card

    The hand written recipe card says to use a jelly roll pan, but gives its dimensions as 12 x 18 which are actually the dimensions for a half-sheet pan which is larger. These pans are easily confused, but there is actually quite a bit of difference in size and your recipe will turn out differently depending on which you use. After making this recipe I believe the intended pan is a jelly roll pan and not a half-sheet. Therefore, the correct pan dimensions will be somewhere right around 15 x 10 or slightly less.

    Also, the hand written recipe card says to use 1 box (2 lb.) of powdered sugar for the icing. I can assure you that it should say 1 box (1 lb.) of powdered sugar for this recipe. It was impossible to even attempt to incorporate 2 lbs. of sugar in the mix. Since I had followed the handwritten recipe and added 2 lbs. of powdered sugar and found that it was way too much, I simply doubled all the rest of the ingredients and made a double recipe of the icing. I spread the entire double recipe of icing on top of the brownies, which gave it an extra thick fudgy topping. Next time I might just do it on purpose, it turned out great!

    Now that we know how to make them, let's bake some old fashioned brownies!

    Two brownies stacked on top of each other on an orange plate

    20 Minute Sheet Cake Brownies With Fudgy Icing

    Nancy Blackstone
    These thin brownies with a thick fudge frosting are a chocolate treat that can be shared with friends and family.
    5 from 4 votes
    Print Recipe Pin Recipe
    Prep Time 10 mins
    Cook Time 20 mins
    Total Time 30 mins
    Course Dessert
    Cuisine American
    Servings 35 2" x 2" Brownies
    Calories 223 kcal

    Ingredients
     
     

    Brownies

    • 2 cups flour
    • 2 cups sugar
    • 2 sticks butter ½ pound
    • 4 tablespoons unsweetened cocoa powder
    • 1 cup water
    • ½ cup milk
    • 1 tablespoon vinegar
    • 2 large eggs
    • 1 teaspoon baking soda
    • 1 teaspoon vanilla extract

    Icing

    • 1 stick butter 8 tablespoons
    • 4 tablespoons unsweetened cocoa
    • 6 tablespoons milk
    • 1 pound powdered sugar
    • 1 teaspoon vanilla
    • 1 cup chopped pecans

    Instructions
     

    • Preheat oven to 400 degrees. Spray jelly roll pan with non-stick cooking spray.

    Brownies

    • In a large bowl, mix the flour and sugar together and set aside.
    • Add 2 sticks of butter, 4 tablespoons of cocoa and 1 cup of water to a saucepan. Mix and heat over medium heat just until it begins to boil. Add to flour/sugar mixture and mix well. 
    • Add 1 tablespoon of vinegar to ½ cup of milk and stir. Mix in with the flour mixture.
    • Add eggs, baking soda and 1 teaspoon of vanilla to batter and combine well. 
    • Pour batter in a 10 x 15 jelly roll pan and bake for 20 minutes.

    Icing

    • While brownies are baking, melt 1 stick of butter in a saucepan. 
    • Add 4 tablespoons of cocoa and 6 tablespoons of milk and mix well.
    • Remove from heat and stir in 1 pound of powdered sugar, 1 teaspoon of vanilla and 1 cup of pecans. Apply frosting on brownies as soon as they are removed from the oven.

    Notes

    For best results use a 10 x 15 jelly roll pan to bake brownies
    Margarine can be substituted for butter
    Walnuts or other nuts can be substituted for pecans in the icing, or you can eliminate the nuts altogether 
    If you prefer a thicker layer of icing, double the icing recipe

    Nutrition

    Calories: 223kcalCarbohydrates: 31gProtein: 2gFat: 11gSaturated Fat: 5gPolyunsaturated Fat: 1gMonounsaturated Fat: 4gTrans Fat: 1gCholesterol: 32mgSodium: 108mgPotassium: 53mgFiber: 1gSugar: 25gVitamin A: 269IUVitamin C: 1mgCalcium: 16mgIron: 1mg
    Keyword 1950's brownies, 1960's brownies, Brownies, chocolate, Fudge, fudge brownies, iced brownies, Jelly Roll Pan, Vintage Brownie recipe
    Tried this recipe?Let us know how it was!
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    Comments

    1. Courtney Collins says

      June 13, 2021 at 6:52 pm

      This is a nice fluffy cakelike brownie thats not overly sweet. First time I didnt frost only added chopped PB cups. I bet the frosting takes it to the next level. Great recipe.

      Reply

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    Nancy and Bentley

    Hi, I'm Nancy! Welcome to Flourchild where I share classic mid-century recipes from the 1940's - 1970's. I feature many vintage handwritten recipes, and provide modern shortcuts and a variety of healthy and special diet-friendly versions whenever possible. Join me in exploring the delicious flavors and from-scratch cooking techniques of our past!

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