Preheat your oven to 180C/350F/Gas 4 and spray three 9-inch round cake pans with baking spray. Set aside.

Sift or whisk together the flour, cocoa powder, baking powder, baking soda, and salt into a bowl. Set aside.

Place the water and sugar into a medium saucepan over medium-high heat. Bring to the boil and stir until the sugar is dissolved. About 1 minute.

Remove pan from the heat and whisk in the chocolate and butter until melted and combined.

Whisk in the oil and vanilla extract.

Crack the eggs into a mixing bowl and whisk together. Slowly add some of the hot chocolate mixture to the eggs, whisking continually to temper them and to avoid scrambling.

Add the now warmed up eggs to the rest of the hot chocolate mixture and whisk to mix well.

Gradually whisk in the dry ingredients until combined.

Fold in the chopped walnuts.

Divide the batter between the three prepared round cake pans.

Bake cakes for 30-35 minutes or until an inserted toothpick comes out clean.

Leave the cakes to cool for 5 minutes before turning out onto a wire rack to cool completely before decorating.

When the cakes have cooled cut the domes off the tops of the cake to make even layers.

To make the vanilla frosting, use an electric handheld or stand mixer and add the butter, powdered sugar, vanilla, and cream to a mixing bowl and beat until combined and smooth.

Use a small amount of frosting to stick the first layer of the cake down onto a 10-inch cake board.

Scoop 1 cup of the vanilla frosting onto the cake layer and use a spatula to spread out evenly.

Place the second cake layer on top and spread the remaining vanilla frosting onto this layer.

Place the third cake layer on top and using a cake scraper or spatula scrape around the sides of the cake to smooth the excess frosting. You can use this excess frosting to crumb coat. Place in the fridge for about an hour to firm up.

To make the chocolate frosting, use an electric handheld or stand mixer and add the butter, and cream cheese, and beat until combined and smooth.

Gradually mix in the dark chocolate cocoa powder, vanilla, and salt.

Slowly, beat in the powder sugar until combined.

Whisk in the heavy whipping cream until the frosting is smooth and peaks can form.

Scoop 1 cup of chocolate frosting into a large piping bag fitted with a large star tip and set aside.

To make the walnut chocolate topping, mix together the chopped walnuts and mini chocolate chips in a bowl until combined. Set aside.

Use the remaining chocolate frosting, and frost the entire cake - sides and top. Use a cake scraper or spatula to get a smooth even finish.

Coat the bottom of the cake with the walnut chocolate topping - reserving a small amount for sprinkling on top of the cake.

To make the chocolate ganache, place the chocolate chips into a heat-proof bowl.

Place the cream in a small saucepan on medium-high heat until steaming.

Pour the hot cream over the chocolate chips and leave to sit for 1 minute before whisking until smooth.

Pour the ganache into a large squeeze bottle and leave to cool for 10 minutes.

Squeeze the bottle of chocolate ganache around the top edges of the cake to form a drip effect and fill in the top of the cake too.

Leave the chocolate ganache to set for about an hour.

To finish the cake, use the piping bag of chocolate frosting to pipe eight swirls around the top of the cake and sprinkle with the reserved walnut chocolate topping.

Chill before slicing and serving. Enjoy!