Recipe: Jack in the Box Cake by Thy Caketh’s Jessamie Holmes

This story appears in our July 2025 Nostalgia issue, presented by Up, where we asked 13 professional bakers to recreate cakes from the iconic The Australian Women’s Weekly Children’s Birthday Cake Book.

Bake vanilla cake mix as per the packet instructions, stirring through the finely grated zest of two lemons before pouring into the tin. Then follow original assembly instructions until it comes to icing.

Sour cream Swiss meringue buttercream ingredients

125g egg whites (just get as close as you can here; usually about 3–4 eggs, separated)
150g caster sugar
250g unsalted butter, cubed, softened
150g sour cream (full fat), room temperature
Pinch of salt
Pinch of cream of tartar (optional)

Sour cream Swiss meringue buttercream method

Start by wiping your bowl, whisk, spatula (anything that the egg whites will touch) with some white distilled vinegar. This will cut through any grease or fat that could spoil your meringue!

Mix together the egg whites and caster sugar in a heatproof bowl.

Place this over a pot of simmering water, stirring often, until the sugar has completely dissolved (it should be smooth with no visible sugar granules).

If you have a stand mixer, great – use the whisk attachment, add a pinch of cream of tartar (optional, it just gives a more stable meringue) and whisk on a medium-high speed until stiff peaks are formed. If you don’t have a stand-mixer, you can do this with an electric hand whisk. (I’ve never tried to whip meringue without electricity … but it has been done, historically.)

Now, add the butter – yep! all at once! – but make sure it’s soft; easy to squish, but not oily or melty!

Whisk again on the highest speed. At this point, I like to avert my eyes – this part can look a little ugly, but rest assured, with enough high-speed whisking, it will come together.

Once it’s all combined and fluffy, you’ve made Swiss meringue buttercream!

But my Eastern European heritage compels me to add sour cream to all my bakes. So, add your sour cream (must be at room temp!) and whisk again. Add salt to taste.

If your mixture looks split or curdled at any point, this just means the ingredients weren’t all at the same temperature; this can happen if you add something like butter or sour cream that is a bit too cold. Easy fix, though! Just get all or some of your mix and microwave it (very briefly, in 10-second bursts) and whisk on a high speed again. It’ll come back.

Assembling the cake

Apply a thin layer of sour cream Swiss meringue buttercream (aka SCSMBC) over the whole cake to lock in the crumbs (a “crumb coat”.) Place this in the fridge to firm up a bit.

Now apply a thicker layer of SCSMBC, using a palette knife to get it as smooth as you can. (Don’t try to get it perfect, it will drain you – remember texture is beautiful!)

Take an ice-cream cone and break it so it’s just the small top. Then use a Microplane grater (gently) to get a neat edge. Place this on the top of your cake like a party hat. Add clown nose with a mini M&M.

On a separate plate, spread a thin layer of SCSMBC over a Salada cracker.

Chill everything in the fridge until completely cold and firm to touch.

Decoration

Using a piece of baking paper as your paint palette, mix some edible lustre dust – find in some supermarkets or specialty baking stores like Miss Biscuit – with something like vodka (that evaporates quickly) to create a paint-like consistency.

Use a small, clean paint brush to apply a harlequin pattern (or whatever you’d like) to the box and Salada cracker (lid), as well as some facial features and make-up. Paint the cone hat, too, if you’d like.

For piping trim around the box, I mostly used a small leaf tip on my piping bag, then a tiny petal tip for around the hat.

Cut a slit near the top edge of your cake (at an angle) and gently push the lid in. Reinforce using your piping bag filled with SCSMBC, particularly at the back.

Pipe along all the edges, then apply a small strip of lace or ribbon for the collar.

The jack in the box cake recipe first appeared in the The Australian Women’s Weekly Children’s Birthday Cake Book, published in 1980.