Chocolate Spider Web Sheet Cake

A simple and bewitchingly moist chocolate sheet cake to sink your teeth into, topped with yummy chocolate ganache and a ridiculously easy spider web decoration. This a

You know that feeling when you really want cake, but don’t want to deal with the fuss of layers and crumb coats, 8 billion cupcake cases and a cloud of icing sugar all over the kitchen?

Enter the wonderful sheet cake!

Sheet cakes (or tray bakes, depending on where you are in the world) are so easy and quick. They’re the perfect solution for those times when you need an amazingly yummy cake NOW without the fuss.

And this chocolate spider web sheet cake is the perfect way to bring a little spooky cuteness to the season.

Top view of chocolate sheet cake decorated with a simple white spider web icing, on a white table with some Halloween decorations in the background

Things I love about sheet cakes

  • sheet cakes the ultimate one bowl bake
  • since sheet cakes are so much thinner than regular cakes they bake faster. Which means you get to eat it sooner.
  • you can just dump all the frosting in the center and spread it all out – soooo much easier to deal with!
  • all those straight lines make sheet cakes easier to portion and cut
  • they’re delicious, nostalgic and super comforting
a square piece of chocolate sheet cake on a white and yellow place with the rest of the spider web cake in the background

I really love Preppy Kitchen’s beautiful Spider Web Cake, but I really wanted one without buttercream.

The things is, I’m not always in the mood for American buttercream. That sugary hit is a good classic, but I wanted something even simpler.

Mostly, I didn’t want to clean powdered sugar from all my kitchen surfaces.

So I’ve gone with a lovely, fudgy chocolate ganache frosting, which sounds all fancy, but it’s actually incredibly simple!

If you’re looking for a simple, unfussy chocolate cake that really delivers on chocolatey flavor then this is it.

close up of a square piece of chocolate sheet cake against a white background

The chocolate cake

The chocolate sheet cake recipe is adapted from Ina Garten’s classic, Beatty’s chocolate cake.

It’s rich, moist, and fudgy.

There’s some buttermilk in there for that wonderful tang and a tender crumb, but if you can’t get your hands on buttermilk I’ve got a great tip for you.

Buttermilk substitution hack

For every cup of buttermilk, measure out just under one cup of regular milk. Add a tablespoon of vinegar to bring the measure back up to a cup, give it a quick stir, and let it sit for a couple of moments. The acid in the vinegar will start to thicken the milk, and makes a perfect substitute for buttermilk!

I almost always use that hack because I never think to buy buttermilk when I’m at the store!

The secret ingredient in this recipe is a cup of freshly brewed coffee. I promise you you won’t taste it in the cake, but it really helps to bring out the deep chocolatey flavors. And it gives the cake that beautiful dark color.

If you’re serving this to kiddos and don’t want to add the coffee you could substitute a cup of water or milk, or even a cup of cocoa if you want to be really decadent!

Word of warning – this cake batter is extremely liquid! Don’t freak out about how runny it is, it will all bake up into the most deliciously moist, rich and yet light chocolate cake.

top view of a square piece of chocolate sheet cake on a white and yellow place with the rest of the spider web cake in the background

Chocolate ganache

Oh, chocolate ganache.

It’s beautifully decadent and delicious and is the perfect topping for that wonderful chocolate cake.

I feel like ganache sounds all fancy and complicated, but the truth is that it’s quick and easy, and you only need 2 ingredients to create this beautiful stuff.

Ok, there are 3 ingredients in the recipe card but, just like in the cake, the coffee is optional. It brings out the chocolate flavor but you can leave it out and you’ll still have an amazing ganache.

But all you really need is heavy cream and semisweet chocolate.

I like to let the ganache cool ever so slightly so it’s more spreadable than runny when I cover the cake. But don’t let it firm up completely, you want it to still be warm.

adding a marbled spider web pattern onto chocolate ganache

White Icing

This is as tricky as the cake gets, and honestly, it’s not hard!

But this is the most important step because without it you’ve got a chocolate sheet cake instead of a chocolate spider web sheet cake! Admittedly, it’ll still be delicious, but the spider web marbling gives it such a fun Halloween twist.

The trick is to work quickly and have things organized.

Prepare the icing while the chocolate ganache is melting. You might need to adjust the water to get the right consistency. You want it to be a thick, pourable consistency that falls off the spoon in thick ribbons.

If your icing is too thick, add a little more water a few drops at a time until it looks right. If you go too far and end up with something too runny add a little more powdered sugar.

I used a no.3 piping tip for this, but I might try a no.4 next time for more defined lines.

top view of chocolate spider web sheet cake for halloween

Tips for creating the marbled spider web design

  • Make sure your cake is at room temperature when you pour over the chocolate ganache.
    The ganache needs to still be fluid when you pipe and marble the white icing. If it’s set or starting to set
    If your cake has been hanging out in the fridge until you’re ready to decorate it be sure to give it time to come back to room temperature before you start on your ganache.
  • Have everything ready before you start to glaze the cake.
    The easiest way to do this is to prep things while the chocolate ganache is melting.
    So get your white icing made and ready to put in the piping bag as soon as the ganache is on the cake.
    Put your cake on your serving platter (if you’re using one – as you can see I just left mine on the baking parchment!).
    And get your cocktail stick ready and by the cake! I can’t tell you how many times I have forgotten this and had to do a mad dash around the kitchen to find mine so I can marble before everything sets.
  • Work quickly and pipe the white icing as soon as you’ve added the ganache.
  • Keep your stokes light and try not to dig into the actual cake as you drag your lines out otherwise you might end up dragging cake crumbs across the surface.

Chocolate Spider Web Sheet Cake

A simple and bewitchingly moist chocolate sheet cake to sink your teeth into, topped with a fudgy chocolate ganache and spider web design.
Course Dessert
Keyword Cake, Chocolate, Halloween
Prep Time 30 minutes
Cook Time 45 minutes

Equipment

  • 9 x 13" pan
  • Cocktail stick/Toothpick or skewer
  • Piping bag

Ingredients

Chocolate Cake

  • 225 g / 8 oz / 1¾ cups all purpose flour
  • 350 g / 12.5 oz / 1¾ cups granulated sugar
  • 1 tsp baking powder
  • tsp baking soda
  • 1 tsp kosher salt
  • 75 g / 2.75 oz / ¾ cup cocoa powder
  • 225 g / 8 oz / 1 cup buttermilk
  • 115 g / 4 oz / ½ cup vegetable oil
  • 2 eggs
  • 1 tsp vanilla extract
  • 225 g / 8 oz / 1 cup hot coffee (substitute same amount of chocolate milk or hot chocolate if you want to make it more kid friendly)

Chocolate Ganache Glaze

  • 115 g / 4 oz / ½ cup heavy cream
  • 225 g / 8 oz / 1 cup semisweet chocolate
  • 1 tsp instant coffee granules (optional)

White Icing

  • 60 g / 1 oz / ¼ cup powdered (icing) sugar
  • ½ tbsp water

Instructions

Chocolate Cake

  • Preheat oven to 350°F/175°C. Grease and line a 9×13 inch pan with parchment paper.
  • In a medium bowl, sift together the flour, cocoa powder, baking soda, baking powder, sugar and salt and mix until combined.
  • In another bowl, add the buttermilk, oil, eggs and vanilla and whisk to combine.
  • Pour the wet ingredients into the dry and whisk them together, scraping the bowl down as needed. Pour in the hot coffee and continue mixing until smooth, but be careful not to overmix!
  • Pour the batter into the pan and bake for 35-45 minutes, until a toothpick inserted in the center comes out clean.
  • Let cake in the tin for about half an hour, then turn it upside down onto a cooling rack and leave to cool completely.

Chocolate Ganache Glaze

  • Chop the chocolate into pieces.
  • Set a bowl over a saucepan of simmering water (a bain marie), and pour in the cream.
    Add the chopped chocolate and instant coffee granules to the cream.
  • Stir occasionally until all the chocolate melts and the mixture combines and becomes smooth and glossy.

White Icing

  • Combine the powdered sugar and the water and whisk together until thick and smooth. The mixture needs to be barely pourable, and when you lift the whisk out of the bowl the icing should slowly fall off the whisk in a ribbon.
    If your mixture is too thick add a few more drops of water until you reach the correct consistency.
  • Transfer to a piping bag fitted with a small round tip, or with the tip of the bag snipped off.

To assemble

  • Take the room temperature cake and pour the ganache evenly over the top, making sure to cover the whole surface of the cake.
  • Before the ganache glaze sets, pipe the white icing in a tight spiral or in concentric circles over the surface of the ganache.
  • With a toothpick or skewer, start at the center of your spiral and drag lines outwards. Repeat all the way around to create the webbed look.

Pin this recipe for later!

Easy, delicious chocolate sheet cake recipe has a fun Halloween twist, with a fun spider web decoration over the simple chocolate ganache frosting. This homemade 9x13 inch cake recipe uses buttermilk to keep things moist and fudgy, and a secret ingredient to bring out that chocolatey flavor! This is a great recipe to use whether you're celebrating a Halloween birthday, or just want a simple old fashioned chocolate cake that you can make with store cupboard ingredients.

Looking for more Halloween recipes?

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It includes two Trick or Treat Halloween banners, straw flags, treat bag toppers, cupcake toppers and more!

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