Instructions

1. Raspberry cake
   Grease and line a quarter sheet pan (9 by 13 inches) with baking or parchment paper. Preheat oven to 180 C (350 F) standard / 160 C (320 F) fan-forced.
2. In a large mixing bowl, add butter, sugar and vanilla and beat with an electric mixer on medium speed until smooth and creamy. Add eggs, one at a time, and beat after each addition.
3. In a separate bowl, add flour, baking powder and salt, and whisk briefly. Add half of the flour mix and all the milk and beat on a low speed until combined.
4. Add remaining flour mix and sour cream and continue to mix on a low speed until just combined and a thick, creamy cake batter forms. Gently fold in raspberries by hand, being careful not to overmix. 
5. Pour cake batter into prepared cake pan and bake in the oven for approximately 30 minutes or until golden on the edges and a knife inserted in the middle comes out clean. Leave cake in pan to cool completely.
6. Vanilla buttercream
   To make your frosting, roughly chop butter into cubes and place in a large mixing bowl. Beat with an electric mixer on medium speed for 1-2 minutes or until your butter is smooth and creamy. There should be no lumps. Scrape down the sides of the bowl.
7. Add vanilla and beat briefly to combine. Then add 125 grams (1 cup) sugar. Beat on a low speed to combine, then turn up the speed to medium and mix for 30 seconds or so. Mixture should be thick and appear a little dry – this is fine.
8. Next, add another 125 grams (1 cup) sugar, along with 1 tablespoon of milk. Beat on medium speed until combined. Scrape down the sides of the bowl.
9. Add another 125 grams (1 cup) sugar, along with 1 tablespoon of milk. Beat on medium speed until mixture is thick and creamy.
10. Finally, add remaining 125 grams (1 cup) sugar and beat on medium speed until mixture is smooth. Buttercream should be lovely and thick at this stage with no lumps. If the buttercream is too thick, add an extra tablespoon or two of milk. 
11. Raspberry sauce
    In a small saucepan, add raspberries, sugar and water. Place on a low heat, and stir continuously, for 5-8 minutes until raspberries melt and a thick syrup forms. Add a squeeze of lemon to taste. 
12. Use a sieve to strain raspberry sauce and discard raspberry seeds. Raspberry sauce should be lovely and smooth.
13. Milk soak
    Combine milk and vanilla extract together.
14. To assemble
    Gently remove cooled cake from pan and remove baking paper. Cut out three 6-inch layers using a 6-inch cake ring. Note the diagram above – you’ll get two whole layers and then two halves.
15. Place a 6-inch cake ring on a cake board or plate. Line the inside of the cake ring with a sheet of acetate. Place the two half pieces of cake at the bottom. Press down the cake firmly. If there are any gaps, use extra cake scraps to fill in the holes and press down very firmly to make one even layer.
16. Spoon 1-2 tablespoons of the milk soak over the first cake layer. Add 1/3 of the vanilla buttercream and spread into one layer. Spoon over a few tablespoons of raspberry sauce. Add a handful of fresh raspberries.
17. Add another layer of cake and press down firmly. Spoon over 1-2 tablespoons of milk. Add 1/3 of the vanilla buttercream. Spoon over a few tablespoons of raspberry sauce. Add a handful of fresh raspberries.
18. Add final cake layer and press down firmly. Add the rest of the buttercream and the remaining raspberry sauce and fresh raspberries. Place cake in the fridge for at least 1 hour to set.