Vegan Black Velvet Sheet Cake (Halloween Monster Cake)

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If you’re looking for the ultimate Halloween dessert that’s equal parts cute, spooky, and delicious, this vegan Black Velvet Sheet Cake is it. Made with black cocoa powder for that signature jet-black colour and rich chocolate taste, this simple sheet cake is tender, decadent, and surprisingly easy to make. Decorated with colourful buttercream monsters and candy eyes, this Halloween monster cake tastes even better than it looks!

Vegan black velvet sheet cake with buttercream monster decorations with four slices cut.

This vegan black velvet sheet cake (or traybake cake) is perfect for Halloween! It consists of a rich, dark black velvet chocolate cake topped with black cocoa chocolate buttercream.

The colourful monster design is totally optional of course but is easy to do with some coloured vanilla buttercream, a few different piping nozzles and some edible candy eyes. The design is inspired by Cloudy Kitchen who made an incredible looking cake over on Instagram so all thanks to Erin for the design inspo!

Why You’ll Love This Vegan Black Velvet Cake:

No food colouring needed to make the deep black colour - it all comes from using black cocoa powder! This also means it won't turn your mouth black when you eat it! (You will need food colouring to make the monster design however).
Rich, mellow, Oreo flavour - black cocoa powder is the main ingredient in Oreo cookies, so this black velvet cake tastes like Oreo in cake form.
Soft, velvety texture - the cake crumb is velvety soft and moist yet light.
Easy to make. The vegan black velvet cake is a one-bowl recipe that is so simple to make, and the black chocolate buttercream is very straightforward as well.
Perfect for Halloween. Whether you create the monster decorations, or just top the cake with chocolate buttercream, it's deep, almost black colour is perfect for Halloween parties.
Ideal for a crowd. This cake will serve up to 24 people.

A labelled photo of the ingredients needed to make vegan black velvet sheet cake.

Ingredients for Vegan Black Velvet Sheet Cake:

Black cocoa powder: This is what gives the cake and chocolate buttercream their rich, black colour. Black cocoa is more heavily alkalised than regular Dutch processed cocoa, so it has a much darker colour and more mellow flavour (like Oreo’s). You can use regular Dutch processed cocoa instead, but you will not get the same level of dark colour. The colour and flavour will vary a bit depending on which brand you use, I used deZaan. You are unlikely to find black cocoa in regular supermarkets so will probably have to order it online.

Oil: Any neutral flavoured oil that is liquid at room temperature will work, I use olive. Do not use coconut oil.

Baking powder and soda: Make sure that you use both, they are not interchangeable.

Light brown sugar: Brown sugar adds flavour and moisture. Caster/granulated will work, but do use light brown if you have it. You will also need icing (powdered) sugar for the buttercream.

Vegan Greek style yogurt: Replaces the eggs and adds moisture. A thick, Greek style soya yogurt is best, though a regular plain yogurt should also work ok.

Milk: I recommend using soya milk as it has the highest protein content. Others such as oat or almond will work but the texture may vary.

Vinegar: This helps the cake rise and tenderises the crumb. I use either apple cider or white wine vinegar.

Coffee: Intensifies the chocolate flavour without making the cake taste like coffee. You can use either freshly brewed or instant coffee but it should be hot when added to the batter. You can use hot water instead but you will be missing out on flavour.

Vegan block butter: You must use a block style vegan butter for the buttercream, not the spreadable kind in a tub which is likely to split due to the higher water content. I like Naturli vegan block or Flora plant butter.

Halloween monster decorated black velvet sheet cake on a black surface surrounded by candy eyes.

How To Make Vegan Black Velvet Sheet Cake:

(Full measurements and instructions can be found in the recipe card at the bottom of the page)

Step 1, the milk, vinegar and yogurt mixture in a bowl.

Step 1: Mix together the soya milk and vinegar in a large bowl, set aside for a couple of minutes to curdle then whisk in the yogurt.

Step 2, the wet ingredients with the cocoa powder added.

Step 2: Whisk in the oil, vanilla and sugar, followed by the cocoa powder, baking powder, bicarbonate of soda and salt.

Step 3, the batter with the flour added.

Step 3: Stir in the plain flour.

Step 4, the batter with the coffee added, in the cake tin.

Step 4: Add the hot coffee and stir until combined then pour the batter into a lined 23 x 33cm tin.

Step 5: Bake for 40 minutes.

Step 6, the butter and icing sugar whisked together.

Step 6: To make the buttercream, whisk the butter with an electric mixer until smooth. Add the icing sugar and vanilla and whisk for a good few minutes until very light and fluffy.

Step 7, the buttercream with the cocoa powder added.

Step 7: Sift in the cocoa powder, add the milk and whisk until smooth.

Step 8, the buttercream spread on top of the cake.

Step 8: Spread the buttercream over the top of the cooled cake.

The ingredients and equipment needed to make the Halloween monster decorations.

How to Decorate a Halloween Monster Cake:

To create the easy monster design, you will need:

Candy eyes. These are often not vegan so be sure to check the packet. The ones I used are vegan as far as I can tell, but you can also make your own if you want to be 100% sure.
Gel food colourings. Use gel rather than liquid colourings to avoid risking the buttercream splitting from adding too much liquid. Rainbow Dust ProGel food colourings are all vegan friendly, as are most Sugarflair ones.
Piping bags. You will need multiple piping bags depending on how many different colours of monsters you want to create. Disposable ones are fine.
Piping bag couplers. You will need as many piping bag couplers as you use piping bags so that you can easily switch piping nozzles.
Piping nozzles. You will need a few different nozzles to create the different piping effects, a grass one for the shaggy monsters, a small open star and a small plain round one. I also used a small closed star one for the wiggly monsters. You can get creative with what you have though!
Vegan block butter, icing (powdered) sugar and vanilla extract to make the buttercream.

Start by making a simple vanilla buttercream. Divide the buttercream into as many small bowls as colours you want - I recommend four different colours. Stir in gel food colouring a little at a time until you reach your desired shades.

The coloured buttercream in small bowls.

Transfer each colour of buttercream to a piping bag fitted with a coupler and piping nozzle of your choice. Pipe designs randomly on top of the cake, washing and swapping round the piping nozzles to make different designs of each colour.

Close up shot of a buttercream monster being piped.

Add candy eyes to make them come alive! Give each one different numbers of eyes and make them as wonky as you like to add personality. If there are any gaps in-between the monsters you can press some eyes into the chocolate buttercream underneath to fill them in.

The decorated monster cake with the piping bags of buttercream around it.

Vegan black velvet sheet cake on a sheet of baking paper surrounded by candy eyes.

Top Tips:

USE SCALES. As with all of my baking recipes I really do recommend using the metric measurements with a digital scales rather than the cup conversions. Cups are a wildly inaccurate measuring system and you will get far better, more consistent results using a scale, not to mention that it is also easier and less messy than cups!

For the teaspoon and Tablespoon measurements, please use proper measuring spoons, not just regular spoons. A teaspoon is 5ml and a Tablespoon is 15ml.

Allow the cake to cool completely before decorating it otherwise your buttercream will melt.

For a more chocolatey flavour, you can swap 30g of the black cocoa powder in the cake for regular Dutch processed cocoa (not natural/cacao).

When you first make the chocolate buttercream it will be more of a dark brown colour than black, be patient and the colour will darken over time. If you want to guarantee a truly pure black colour then you can add a little black gel food colouring (I didn't add any to mine).

Candy eyes tend to be very hard so are not suitable for small children. I would recommend making your own if you are serving this cake to children.

Close up shot of the buttercream monsters.

FAQs:

Where can I get black cocoa powder?

You are very unlikely to find black cocoa powder in stores so will probably have to order it online. I used this one by deZaan but you can also find various brands on Amazon. You can also use regular Dutch processed cocoa powder but will not get the same dark black colour.

What makes this a “velvet” cake?

Recipes for "velvet" cakes, so called because of the fineness of their crumb texture, date to the 19th century. Today, there are recipes for virtually every colour of velvet cake – red velvet being the most popular. The common denominator between most velvet cake recipes is the use of buttermilk or vinegar. These acidic ingredients help give the cakes their velvety texture.

How should I store it?

This vegan black velvet sheet cake will keep in an airtight container at cool room temperature for up to 4 days. If it is very warm out keep it in the fridge, allow to come up to room temp before serving.

Can I freeze it?

The un-iced cake can be frozen for up to 3 months. Wrap it well before freezing to prevent freezer burn.

I don't recommend decorating the cake and then freezing it in advance of serving, but any leftovers can be frozen. Allow to defrost at room temperature to serve.

A slice of vegan black velvet sheet cake on a metal plate with a fork.

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