Method

• 1.
  To make candied thyme, place 1 cup (220g) caster sugar and eggwhites in separate bowls. Gently brush eggwhites onto lemon thyme sprigs, 1 sprig at a time, shaking off excess, then dip in caster sugar. Place on a wire rack and stand for 6 hours to overnight or until dry.
• 2.
  Preheat oven to 160°C. Grease base and sides of three 15cm round cake pans and line with baking paper. Place chocolate and butter in a heatproof bowl over a saucepan of gently simmering water (don’t let bowl touch the water) and stir until melted and smooth. Stand for 5 minutes to cool slightly.
• 3.
  Meanwhile combine buttermilk, flour, egg, yoghurt and remaining 300g caster sugar in a bowl. Add chocolate mixture and whisk until smooth. Divide among prepared pans and bake for 1 hour 5 minutes or until a skewer inserted into the centre comes out clean. Stand in pans for 30 minutes, then invert onto wire racks to completely cool.

• 4.
  For the cream cheese filling, using a stand mixer fitted with the paddle attachment, beat all ingredients on high speed until very smooth. Set aside.
• 5.
  Trim tops of 2 cakes to level and place 1 trimmed cake on a cake stand. Spread top with 1 cup (220g) frosting and sprinkle with half the biscuits. Top with another trimmed cake and repeat the process. Top with untrimmed cake and spread all over with a very thin layer of frosting. Freeze for 10 minutes to set. Spread with remaining frosting and smooth with a spatula. Top with candied lemon thyme to serve.