The Best 9×13 Chocolate Cake from Scratch

Most chocolate cakes from scratch disappoint — they’re dry, one-note, or just fine. I tested this one four times to fix that, landing on both cocoa powder and melted bittersweet chocolate for real depth, oil instead of butter for moisture that lasts, and hot coffee to make the chocolate actually taste like chocolate. Make it once and it will become your go-to recipe.

Why This Recipe Is Different

I tested this cake four times before I called it done, and each batch taught me something specific. I started by combining the best elements from two recipes I already loved. The first test was too dry. The second was better but bitter because I used unsweetened chocolate instead of bittersweet. I was getting closer, but I was not there yet.

Test three is where everything shifted. I dropped the butter entirely and went all oil, increased the cocoa powder, swapped hot water for hot strong coffee, and switched to bittersweet chocolate. The result was honestly so good I almost stopped there. Light, fluffy, real chocolate flavor. But the crumb was slightly too loose, which told me the structure was not quite right.

One more egg and a little less coffee fixed it. That is the difference between test three and the final recipe, and it is why I do not skip steps when I am developing something. Small adjustments matter.

The other thing worth explaining is why this recipe uses two sources of chocolate instead of one. Cocoa powder alone gives you a flat, one note chocolate flavor. Melted bittersweet chocolate adds richness and depth that cocoa cannot replicate on its own. Together they give you a cake that actually tastes like chocolate, not just a cake that is brown.

This cake is part of my 9×13 cake series, born from my Instagram audience asking for more one pan cakes they could actually transport and bring somewhere. We already have white cake and lemon cake in this series, and chocolate might be my favorite of the three.

Key Ingredients

Here’s an overview of the key ingredients in this recipe and what they do. Jump to the recipe card below for the full recipe.

• Unsweetened Natural Cocoa Powder: Natural cocoa is more acidic than Dutch process, which means it reacts properly with the baking soda in this recipe. Do not swap them without adjusting your leavening.
• Bittersweet Chocolate Baking Bar: Three ounces of melted bittersweet chocolate adds richness and depth that cocoa powder alone cannot give you. Use a baking bar, not chips. Chips have stabilizers that affect how they melt.
• Buttermilk: Buttermilk tenderizes the crumb and balances the bitterness of the chocolate. No buttermilk? Follow my homemade buttermilk tutorial.
• Hot Strong Coffee: You will not taste it. Coffee blooms the cocoa powder and deepens the chocolate flavor in a way hot water cannot replicate. Use a strong brew or dissolve a teaspoon of instant espresso in half a cup of hot water.
• Vegetable Oil: Oil stays liquid at room temperature, which keeps this cake moist and tender for days. Butter solidifies when it cools and can make cake feel dry the next day.
• 3 Large Eggs: Two eggs made the crumb too loose in testing. Three gives you a tight, moist crumb with enough structure to support the frosting.

Coffee in Chocolate Cake

Let’s just address this directly because I know it comes up. You cannot taste the coffee. Coffee’s job in a chocolate cake is not to add coffee flavor, it is to make the chocolate taste more like chocolate. It amplifies and deepens everything the cocoa powder is doing, and the difference is noticeable. If you are truly opposed to using brewed coffee, use hot water instead, but know that you will get a slightly less intense result. Strong coffee is worth it here.

How to Make Chocolate Sheet Cake

Here are the step-by-step instructions for making the best chocolate sheet cake. You can also jump to the recipe card below for the full recipe.

For the Chocolate Cake

Prep oven and pan: Preheat the oven to 350ºF (180ºC). Grease or line a 9×13 inch baking pan with parchment paper and set aside.

Combine dry ingredients: In a large mixing bowl, whisk together the flour, cocoa powder, granulated sugar, baking powder, baking soda, and salt. Set aside.

Combine wet ingredients: In a separate mixing bowl, whisk together the vegetable oil, melted and cooled bittersweet chocolate, eggs, buttermilk, hot coffee, and vanilla extract until combined.

Combine all: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.

Transfer batter: Pour the batter into the prepared 9×13 inch pan and spread into an even layer.

Bake: Bake at 350ºF for 30-35 minutes, or until a toothpick inserted in the center comes out clean. Note that dark pans will bake faster than light pans, so start checking at 28 minutes if using a dark pan.

Cool: Allow the cake to cool completely in the pan before frosting.

For the Chocolate Frosting

Beat butter: Beat the butter with a hand mixer or stand mixer on medium speed until smooth and creamy, about 2 minutes.

Begin mixing in ingredients: Add the cocoa powder, vanilla, and salt. Mix on low until combined.

Mix in sugar gradually: Add 3 cups of powdered sugar one cup at a time, mixing on low after each addition.

Mix in heavy cream: Add 2 tablespoons of heavy cream and mix on medium speed until fluffy, about 1 minute.

Adjust: Adjust consistency as needed. Add more powdered sugar for a thicker frosting or more milk one tablespoon at a time for a thinner, more spreadable frosting.

Spread: Spread over a completely cooled cake. 

Pan Notes

A 9×13 inch pan is exactly what this recipe is designed for, but not all pans bake the same way. Light colored aluminum pans heat more evenly and give you more control over browning. Dark pans absorb heat faster, so start checking for doneness at 28 minutes if that is what you are using.

How to Know When It’s Done

Start checking at 28 minutes if you are using a dark pan, and at 30 minutes if you are using a light pan. Insert a toothpick into the center of the cake. You are looking for a clean toothpick or one with just a few moist crumbs attached. The edges will also start to pull away slightly from the sides of the pan when it is close to done.

Do not overbake. A dry chocolate cake is a sad chocolate cake, and it happens fast once you go past the window.

Frosting Options

This cake is topped with a classic chocolate buttercream. A 9×13 cake can hold a generous layer of frosting because you are spreading it flat rather than trying to get it to stay on the sides of a layer cake. Go thick. Use an offset spatula or the back of a large spoon and spread it all the way to the edges.

Want something other than chocolate frosting? This cake is a great base for a lot of different frostings. Peanut butter frosting is an obvious match if you love that combination. Oreo frosting is a crowd pleaser every single time. Coffee buttercream leans into the coffee already in the cake and makes the chocolate flavor even deeper. Cream cheese frosting gives you a tangier, less sweet finish that balances the richness really well. Salted caramel frosting is unexpected but genuinely great on chocolate cake. And if you want something a little more fun, peppermint frosting is perfect for the holidays and strawberry cream cheese frosting is a nice option when you want something a little lighter and fruity.

Storage and Make Ahead

This cake keeps well at room temperature, covered, for up to three days. The texture actually gets a little better on day two. If your kitchen is warm, store it in the refrigerator and let slices come to room temperature before eating.

You can freeze this cake unfrosted, wrapped tightly in plastic wrap and then foil, for up to two months. Thaw overnight in the refrigerator and frost when it is fully at room temperature.

If you want to get ahead for an event, bake the cake one day and frost it the day you are serving it. The baked cake keeps well covered at room temperature overnight.

More Chocolate Cake Recipes

• Chocolate Coffee Cake
• Chocolate Zucchini Cake
• German Chocolate Bundt Cake
• Chocolate Raspberry Cake