Giant Picnic cake

Method

• 1
  Preheat oven to 180C/160C fan-forced. Grease three 20cm x 30cm lamington pans. Line bases and 2 long sides of each pan with baking paper, extending paper 2cm above edges of pan.
• 2
  Prepare cakes in batches following packet directions. Pour batter evenly among prepared pans. Bake cakes for 45 minutes or until a skewer inserted into the centre of cakes comes out clean. Stand in pans for 5 minutes. Turn, top-side up, onto a wire rack lined with baking paper. Cool completely.
• 3
  Make Caramel Fudge Ganache: Place chocolate, caramels and cream in a medium saucepan over low heat. Cook, stirring, for 10 minutes or until mixture is smooth and just comes to the boil. Remove from heat. Using food colouring, tint ganache a caramel colour. Set aside for 2 1/2 hours or until ganache has cooled and is thick enough to spread.
• 4
  Meanwhile, make Milk Chocolate Ganache: Place chocolate in a large heatproof bowl. Place cream in a small saucepan over medium heat. Bring to a simmer (do not boil). Pour hot cream over chocolate in bowl. Stir until chocolate has melted and mixture is combined. Set aside for 2 hours or until ganache is cool and a thick, pourable consistency.
• 5
  Make Peanut Crackle: Place chocolate in a microwave-safe bowl. Microwave on HIGH (100%), stirring with a metal spoon every 30 seconds, for 1 to 2 minutes or until smooth. Stand for 2 minutes. Combine puffed rice and roasted peanuts in a medium bowl. Add melted chocolate. Stir until well combined. Stir in Picnic bars. Spoon mixture onto a baking tray lined with baking paper. Set aside for 30 minutes or until firm. Break peanut crackle into small pieces no bigger than 2.5cm.
• 6
  Make Buttercream: Using an electric mixer, beat butter and vanilla for 8 to 10 minutes or until light and fluffy. Gradually add icing sugar, beating until well combined. Add milk. Beat until combined.
• 7
  Trim tops of each cake to level. Trim sides of cakes to remove crusts. Cut 2cm off 1 long side of each cake. Discard trimmings. Place 1 cake on centre of cake board or serving plate. Spread top with 1/4 cup buttercream. Arrange 1/2 the wafers in a single layer over buttercream, pressing gently to secure. Spread 2/3 cup remaining buttercream evenly over wafers. Top with 1 cake, pressing gently to secure. Spread with 1/4 cup remaining buttercream. Top with remaining wafers. Spread remaining buttercream evenly over wafers. Top with remaining cake.
• 8
  Spoon caramel ganache onto cake. Spread evenly over top and sides of cake. Place peanut crackle pieces over top and sides of cake, pressing lightly to secure. Refrigerate cake for 20 minutes or until caramel is firm. (Caramel may slide down the sides of cake as it cools. Use a spatula to spread it back onto the sides of cake.)
• 9
  Pour chocolate ganache over top of cake, allowing it to fall down the sides to cover. Use a spatula to spread ganache over any uncovered parts of the cake. Refrigerate for 30 minutes or until set.
• 10
  Using a spatula, scrape excess ganache from board and wipe with damp paper towel. Refrigerate. Serve (see Notes).