Preheat the oven to 180oC (160oC Fan). Lightly grease a deep 8-inch round cake pan and line the base with a disc of parchment paper.

Add the butter to a saucepan and place over medium heat and cook until the butter is browned. Once the butter has turned a golden brown and has a nutty aroma, pour the butter into a large mixing bowl and allow to cool for a few minutes. Add the sugar to the bowl and whisk to combine. Add the eggs, one at a time, whisking until fully combined before adding the next. Pour in the buttermilk and vanilla and whisk to combine. Add the flour, baking powder, bicarbonate of soda and salt and whisk briefly, just until a smooth cake batter is formed.

Pour the cake batter into the prepared tin and lightly tap on the work surface a couple of times, to knock out any large air bubbles. Bake in the preheated oven for about 40-45 minutes or until the cake springs back to a light touch and is starting to pull away from the sides of the tin. Set aside for 15 minutes before carefully turning out onto a wire rack to cool completely.

For the raspberry filling, place 50g of the raspberries into a mixing bowl and use a fork to mash into a rough puree. Add the jam and mix until combined with the rough puree. Add the remaining raspberries and fold to combine.

When ready to assemble the cake, use a large serrated knife to cut the cake into two even layers. Add all of the ingredients from the mascarpone whip to a large, chilled, bowl and whisk on medium speed until the cream holds soft peaks. Spread about ½-⅔ of the mascarpone filling onto the bottom cake layer. Drizzle over about ½ of the raspberry mixture and roughly swirl it into the cream mixture. Place the second cake layer atop the cream and repeat with the remaining mascarpone whip and raspberries.

Once assembled the cake is best served on the same day. The cake itself can be prepared a day or two in advance, kept wrapped in clingfilm until you are ready to assemble.