Preparation Time: 2-3 hours

Total Time: 3 1/2 hours, plus an additional 1 hour at room temperature prior to serving

INGREDIENTS

Chocolate Cake, adapted from this Donna Hay recipe

• 375 mL water
• 185 g unsalted butter, cubed
• 80 g cocoa powder
• 450 g plain flour
• 1 1/2 teaspoon baking soda
• 600 g caster sugar
• 3 large eggs, lightly beaten
• 185 mL buttermilk
• 2 teaspoons vanilla extract

Chocolate Ganache

• 200 g dark chocolate
• 200 g thickened cream

Cookies and Cream Swiss Meringue Buttercream

• 10 large, fresh egg whites (300 g)
• 500 g white sugar
• 680 g unsalted butter, cut into small cubes and cool, but not cold (leave out of fridge for 15-20 minutes before use)
• 1 teaspoon vanilla extract
• pinch of salt
• 400 g Oreo cookies, pulverised to a fine crumb in a food processor

To Decorate

• 7 Oreos, cut in half
• 100 g chocolate sprinkles

METHOD

Chocolate Cake

1. Preheat oven to 160°C/325°F fan-forced. Grease and line two 18 cm/7 inch cake tins.
2. Combine the water, butter and cocoa in a medium saucepan over medium heat, and stir gently until the butter has just melted.
3. Sift the flour, baking soda and sugar into a large mixing bowl. Pour in the cocoa mixture, eggs, buttermilk and vanilla, and whisk until the ingredients are combined and the batter is smooth. Do not over-whisk, only until the dry ingredients are just incorporated into the wet.
4. Pour the mixture evenly into the two tins. Bang the tins a couple of times on the counter. Bake the cakes on a central rack for 45-50 minutes, rotating them after 30 minutes to ensure even baking. The cakes are cooked when a metal skewer inserted into the centre comes out clean but moist, with a few crumbs but no wet batter.
5. Allow the cakes to cool in their tins on a metal rack for 20 minutes, then turn out and leave to cool completely. Use a sharp serrated knife to slice off the domed tops, and halve the cakes to form 4 layers.

Chocolate Ganache

1. Rougly chop the chocolate and place in a heatproof bowl.
2. Bring the cream to a gently simmer over low heat, stirring often. As soon as a few bubbles start to form, pour the hot cream over the chocolate. Seal the bowl with foil and leave for 10 minutes.
3. Gently whisk the ganache until smooth. Cover again, and refrigerate for at least 2 hours until firm.

Cookies and Cream Swiss Meringue Buttercream 

1. In a large heatproof bowl over a pot of simmering water, gently hand-whisk the egg whites and sugar until sugar has just dissolved and mixture appears white (5-10 minutes). Alternatively, use a candy thermometer to whisk until temperature of mixture reaches 70°C/160°F. Ensure you whisk gently but constantly, so that egg whites do not cook.
2. Transfer mixture to the large bowl of an electric mixer, and whisk on medium/low speed until meringue is thick and glossy and holds its peaks, and the bowl feels neutral to touch. It is very important that you whisk until the bowl no longer feels warm, otherwise the butter will melt when added. Whisk for 10-15 minutes, and if the bowl is still warm, turn mixer off and allow meringue to cool further. This will ensure you do not over-whisk meringue. Double check the temperature of the meringue by turning off the mixer, and dipping a clean finger into the centre of the meringue. It should feel room temperature.
3. Once cooled, swap whisk attachment for paddle attachment. With the mixer on its lowest possible speed, gradually add butter one cube at a time, beating for a few seconds between each addition. The buttercream will suddenly loosen and may appear thin or scrambled as you go, but just keep beating on low speed until all of the butter is incorporated.
4. Once all of the butter is added to the buttercream, continue beating on a low speed for a minute or two. The buttercream should be thick and glossy. If it is too thin, the butter was too soft when added, so refrigerate buttercream for 15 minutes to firm up and then continue beating. If it appears too thick or scrambled (literally like scrambled eggs!) the butter was too cold when added, so keep beating on low speed until buttercream is smooth. Add the salt, vanilla and pulverised Oreos and beat gently until evenly combined.
5. Dollop a spoonful of buttercream on your cake board or serving plate, and secure the first cake layer upside down. Dollop 1 generous cup of buttercream onto the first layer, then spread evenly right up to 1 cm from the edge using a butterknife or small offset spatula. Place the second cake layer down, pressing gently from the centre outwards to spread the buttercream to the edges. Repeat the layering process with the buttercream and remaining cake layers.
6. Using a little of the buttercream, frost a crumb coat over the entire cake. This is a very thin coat, and you should be able to see the cake through the buttercream. It forms a seal around the cake so you don’t get crumbs in your pretty frosting! Refrigerate the cake for 20 minutes, until buttercream is firm to touch.
7. Frost the outside of the cake by dolloping the remaining buttercream on the top surface, spreading it out until it falls over the sides of the cake, and then spreading it evenly around the sides.
8. Refrigerate cake for at least 30 minutes until buttercream is firm to touch. Use a clean metal spatula, butterknife or benchscraper to smooth the surfaces of the cake.

To Decorate

1. Use a 1cm diameter star piping tip to pipe 14 large stars of cooled chocolate ganache around the perimeter of the cake. Place 1 Oreo half in each star.
2. Press handfuls of chocolate sprinkles around the base of the cake.

Store the cake in the refrigerator. Make sure the cake has been out of the fridge for at least 1 hour before serving, to ensure the cake and buttercream are soft and at room temperature.

Store the cake covered and refrigerated for up to 3 days, but best served within 1-2 days of baking. 

Note: The cakes can be made up to 2 days in advance, and stored in an airtight container. Swiss meringue buttercream can be refrigerated in an airtight container for up to one week, or frozen for up to 6-8 weeks, prior to the addition of the cookies. Before using it to frost your cake, allow it to cool to room temperature, then beat on medium speed using an electric mixture until it retains its silky, soft consistency. This can take up to 20 minutes, so be patient if the texture looks a little strange. Beat in the cookies. For ease, if possible prepare the SMB immediately before you frost your cake.