Prepare the Oven and Tray: Preheat the oven to 170°C and line a 12-hole cupcake tray with cupcake liners.
Cream the Butter and Sugar: Beat the cupcake butter and caster sugar in an electric mixer on medium speed for 5 minutes, until the mixture looks light and creamy.
Combine the Dry Ingredients: Sift the self-raising flour and baking powder together in a separate bowl and set aside.
Add the Eggs: Reduce the mixer speed to low and add the eggs one at a time, mixing until each egg is fully incorporated.
Mix the Batter: Add half of the flour mixture and mix until combined. Pour in the milk and vanilla extract, then add the remaining flour, chopped pistachios, and raspberry jam. Mix just until everything is evenly incorporated.
Fill the Cupcake Cases: Divide the batter among the prepared liners using an ice cream scoop or two spoons, filling each case about two-thirds full.
Bake the Cupcakes: Bake at 170°C for 20 minutes, or until the cupcakes are golden brown and spring back when gently touched.
Cool the Cupcakes: Leave the cupcakes in the tray for 5 minutes, then transfer them to a wire rack and allow them to cool completely before frosting.
Beat the Frosting Butter: Place the softened frosting butter in a clean mixing bowl and beat with an electric mixer until pale and soft.
Add the Frosting Ingredients: Add the icing sugar, vanilla extract, and 2 tablespoons of milk. Start mixing on low speed, then gradually increase the speed as the ingredients combine.
Colour and Whip the Frosting: Add a small drop of pink food colouring and whip the frosting for 5 minutes. If it is too stiff for piping, add a little more milk until it reaches a suitable consistency.
Pipe the Cupcakes: Transfer the frosting to a piping bag fitted with an open star nozzle. Pipe a swirl onto each completely cooled cupcake.
Decorate and Serve: Finish each cupcake with chopped pistachios and a fresh raspberry before serving.
