Immensely chocolatey peanut-butter meringue layer cake

This is the most elaborate cake I've ever made, but it was so worth it. It's an amalgamation of 2 recipes, one is a crunchy milk chocolate-peanut butter layer cake (from American Food and Wine)  and the other was a chocolate layer cake from the reliably good BBC Good Food website. I made it for the OH's birthday and it made a great celebration cake - and it's certainly big enough for all the family! The ganache for the top and sides needs to be done well in advance so it has time to thicken up-mine was still a little runny.

The middle is a gorgeously crunchy combination of meringue, nuts and a chocolate-peanut butter-rice crispy set ganache. You need a serrated-edged knife to cut through it to get a clean slice, but if you like a bit of texture it's great, because it provides a nice contrast to the moist sponge.

Messy but good-my ganache was too runny!

Ingredients
For the ganache: 
300ml double cream
300g milk chocolate, chopped

For the sponge: 

• 175g self-raising flour , sifted
• 3 tbsp 70% cocoa powder
• 175g golden caster sugar175g butter , completely softened, plus extra for lining the tin
• 1 tsp baking powder
• 3 large eggs
• 1-2 tbsp milk
• 100g 70% dark chocolate , melted and cooled

• For the middle:
• 25g ground almonds
• 100g icing sugar
• 2 large egg whites
• 1tbsp granulated sugar
• 260g smooth peanut butter
• 25g slivered almonds (or chopped peanuts)
• 2 tbsp butter
• 85g milk chocolate
• 25g rice crispies 

Method (sponge & icing):
1. Make the icing first (it takes a while to cool and thicken). Put the chocolate into a bowl. Pour the cream into a pan and heat until simmering. Take off the heat and pour it over the chocolate. Stir until the mixture is smooth. Cool, then chill, until really thick but spreadable.

2. Heat the oven to 180C/fan 160C/gas 4. Butter and base-line 2 x 18cm sandwich tins with baking parchment. Take 3 tbsp flour from the full flour amount and put them back in the flour bag - the cocoa powder will make up the difference.

3. Put all the cake ingredients except the chocolate in a large bowl. Beat them together with an electric whisk (or whizz in a food processor) until you have a creamy mixture, then fold in the melted chocolate. Add a little more milk if the mix is too stiff - it should fall easily from a spoon.

4. Divide the mixture between the 2 tins and level. Bake on the same shelf in the oven for 20-25 minutes or until the sponge springs back when pressed. Cool for 5 minutes, turn out onto a wire rack, peel off the paper and cool completely. 

Method (cake filling):

1. Trace a 9-by-13-inch rectangle onto a sheet of baking parchment and lay it on a large baking sheet. Mix the ground almonds with the icing sugar. In a bowl, using an electric mixer, beat the egg whites at medium speed until soft peaks form. Add the granulated sugar and beat until the whites are stiff and glossy, about 2 minutes. Using a rubber spatula, fold in the almond mixture. Spread the meringue on the baking parchment to fill the rectangle. Sprinkle the slivered almonds/chopped peanuts on top. Bake for about 20 minutes, until lightly browned and firm. Let cool.
2. In a medium bowl set in a saucepan of simmering water, heat the peanut butter with the butter and milk chocolate, stirring constantly, until smooth and melted. Remove from the heat and fold in the Rice Krispies. Spread the mixture all over the meringue rectangle. Transfer to the freezer and let cool completely.
3. Place the bottom cake layer on a large board. Spread some of the ganache over the cake. Invert the meringue filling (now hard) onto the cake and peel off the paper. Spread some more of the ganache over the filling, then top with the second cake layer. Refrigerate until firm, for at least 1 hour. Remove from the fridge and trim the edges of the meringue mixtures (use a serrated-edge knife) so the middle of the cake lies flat with the sponge. Spread the remaining ganache over the top and sides of the cake and refrigerate to set. Cut and serve.