Preheat the oven to 350°F (175°C) and prepare your cake tin by greasing it lightly.

Cream together the softened unsalted butter and golden caster sugar in a large bowl until light and fluffy, about 3-5 minutes.

Incorporate the vanilla extract and add the eggs one at a time, mixing well after each addition.

Sift the plain flour, baking powder, and fine sea salt into a separate bowl, then gently fold this dry mixture into the wet ingredients until just combined.

Add the shelled pistachios to the batter and fold them in until evenly distributed.

Pour the batter into the prepared cake tin and smooth the top with a spatula.

Bake in the preheated oven for 35 minutes or until a skewer inserted into the center comes out clean.

Cool the cake completely in the tin, then transfer to a wire rack to cool down thoroughly.

For the frosting, beat the softened butter and sifted icing sugar together until creamy and smooth, about 4-5 minutes.

Mix in the smooth pistachio cream, fine sea salt, lemon juice, and raspberry jam until well combined.

Generously frost the cooled cake with the pistachio frosting.

Top with fresh raspberries and sprinkle the chopped pistachios on top.

Garnish with sprigs of fresh mint.