When Hearthe first opened its doors, a rosella basil cake was one of three signature cakes on offer. Many people loved it, but I felt that the texture was somewhat unresolved. The marshmallow was difficult to cut, the cake was too tall, and the rice crispy base didn’t slice cleanly. Although the flavours were lovely, it was clunky to eat. took the cake off the list until I was able to perfect it. This is how Rosella wagon wheels were born.

I used to buy Wagon Wheels at my school canteen. They consist of marshmallow and raspberry jam sandwiched between two biscuits. The whole thing is then dipped in chocolate and eaten with your hands.

As a cake slice, the rosella basil cake may not have worked, but as a wagon wheel, everything just made sense. The cake is much thinner, the marshmallow is sandwiched between the biscuits and – because it is eaten with your hands – you don’t need to cut it.

I’ve included gin in the marshmallow, but feel free to leave this out if you want a kid-friendly version.

Makes 12 wagon wheels

INGREIDIENTS
Basil cake
20g basil leaves
350g caster (superfine) sugar
3g (1/2 teaspoon) fine salt
2g (1/2 teaspoon) baking powder
2g (1/2 teaspoon) bicarbonate of soda (baking soda)
240g plain (all-purpose) flour
200g extra-virgin olive oil
300g full-cream (whole) milk
165g (approx. 3) whole eggs
zest of 1 lemon 

Gin and tonic marshmallow
16g powdered gelatine
145g tonic water
225g caster (superfine) sugar
240g glucose
12g (1/2 tablespoon) gin (optional)
50g rosella flowers, chopped 

Equipment
Twelve egg rings
Twenty-four 8cm cake rings 

Crunchy white chocolate discs
500g white chocolate, roughly chopped
500g feuilletine, softened
500g puffed rice cereal 

Gin basil oil (optional)
Leaves of 1/2 bunch of basil
100g grapeseed oil
100g gin 

To assemble
1 quantity Desert lime ermine
200g raspberry jam
550g white chocolate, roughly chopped
10g dried rosella, diced (optional)
Edible flowers (such as nasturtiums), to garnish 

Substitutions
Rosella > dried hibiscus or rose petals 

METHOD
For the basil cake
Preheat the oven to 180˚C. Grease and line a 30 x 20cm sheet pan.

To make the basil cake, add the basil leaves and sugar to a food processor and pulse until the basil is finely chopped and the sugar has taken on a green colour. Transfer to a bowl, then add the salt, baking powder, bicarbonate of soda and flour. Add the oil, milk, egg and lemon zest and whisk until combined. The batter will appear runny but will bake dry. Transfer to the pan and bake for 20 minutes. The cake will give off a lot of steam which will need to be extracted by keeping the door slightly ajar. If there is too much steam in the oven chamber the cake will puff up and bake irregularly, then collapse.

Remove and leave to cool in the pan before unmoulding. Trim the cake sheet flat and cut out twelve 7.5cm circles with a round cutter.

For the gin and tonic marshmallow
Combine the gelatine and tonic water in a stand mixer fitted with the whisk attachment. Do not turn on just yet. Add the sugar, glucose and 60g of water to a saucepan and stir together well. Brush down the side of the pan with water until no grains of sugar are left above the water line. Cook over a high heat to 114˚C.

Turn the mixer to medium speed and pour in the hot liquid in a steady, slow stream, being careful to avoid the whisk as much as possible. Once the mix has cooled slightly, increase the speed to high and mix until light.

Add the gin, if using, and continue to mix. Fold the chopped rosella through the marshmallow. Oil twelve egg rings and place on a flat baking tray lined with a silicone baking mat. Fill the egg rings with the marshmallow and leave to set in the fridge until required. 

For the white chocolate discs 
To make the crunchy white chocolate discs, add the white chocolate to a heatproof bowl and melt over a bain-marie (deep tray filled with hot water). Add the feuilletine and puffed rice cereal to the melted chocolate and stir to combine.

Line a flat baking tray with a silicone baking mat. Oil the cake rings and place on the baking mat. Pour in the chocolate mixture about 3 mm (⅛ in) thick. Refrigerate until required.

For the gin basil oil
If you are making the gin basil oil, put the basil leaves in a blender. Add the grapeseed oil and blend until smooth and vibrant green.

Add the gin, blend briefly, then transfer to a container. Brush the basil cake discs with the gin basil oil, making sure the syrup penetrates all the way through the cake. 

To assemble
Unmould the chocolate discs and place twelve discs on a baking tray. Spread some desert lime ermine on the discs and stick a basil cake disc to each chocolate disc.

Warm the jam to a spreadable consistency, spread on the cake and stick on a marshmallow disc. Apply more jam to the marshmallow and top with another chocolate disc. Allow to rest in the fridge.

Temper the white chocolate according to the manufacturer’s instructions, add the dried rosella (if using) and mix well.

Dip the bottom third of each wagon wheel into the chocolate and place, standing up, on a piece of baking paper, with the white chocolate on an oblique angle. Allow to set before moving. Garnish with edible flowers. 

Supplementary recipes

INGREDIENTS
Desert lime ermine
60g (1/4 cup) Desert lime syrup (see below)
10g plain (all-purpose) flour
100g butter, softened 

Desert lime syrup
100g desert limes
200g caster (superfine) sugar 

METHOD
For the desert lime ermine
Make the desert lime ermine by adding the desert lime candying syrup to a saucepan and whisking in the flour. Cook over a low heat, whisking continuously, until you have a pudding-like consistency. 

For the desert lime syrup.
Add the sugar to a small saucepan with 200g water and bring to the boil. Remove from the heat, add the desert limes and allow to cool in the pan. Transfer to a container and refrigerate overnight. The next day, strain the syrup and keep the desert limes for use in another recipe.This is an edited extract from Modern Australian Baking by Christopher Thé, published by Hardie Grant Books. Photography by Chris Chen.