1. First make the jam. Blend together the raspberries, jam sugar and vanilla extract in a JTC Omniblend. Pour the mixture through a sieve into a large, non-stick pan and cook until thickened. To test for doneness, place a saucer in the fridge until it’s really cold. Put a teaspoon of jam on the plate and leave for 5 minutes. Push the jam with your finger – if it wrinkles up, it’s reached the setting point. Set aside to cool.
Note: This makes one 500ml jar of jam - you will need 2-3 tbsp for this cake. Stow the rest away in a sterlised jar for toast, scones and of course, more cakes.
2. Preheat the oven to 175°C and grease and line 2 x 8-inch cake tins.
3. To make the sponge, sift together the flour, baking powder and baking soda. Set aside.
4. Whip the butter in a stand mixer until pale. Slowly add the sugar until very pale – about 8 minutes (the longer the better). Next with the mixer on low, add in the vanilla, salt and one egg at a time until each one is incorporated. With the mixer still on very low, add in 1/3 of the flour, combine and add in 2/3 of the buttermilk, combine, 1/3 of the flour, combine, 1/3 of the buttermilk. Finally, stir in the remaining 1/3 flour and mix until smooth. It’s really important to begin and end with the dry ingredients and not to overmix.
5. Bake for 40 minutes or until a skewer inserted into the cakes comes out clean. The top of the cake should be springy to the touch.
6. Remove from the oven and allow to cool in the tins for 10 minutes. Remove the cakes from the tins and place on a wire rack, allowing to cool completely.
7. To make the buttercream, whip the butter until pale, about 3 minutes. Gradually add the sugar and vanilla. Beat until very light and pale, about 8 minutes.
8. Trim the tops of the cakes if necessary. Stack the cakes with jam and buttercream, the ice the outside of the cake with more buttercream.
9. Decorate with marshmallows skewered onto lollipop sticks and retro sweets.