Preheat oven to 180°C/350°F/Gas 4. Spray 3 (9-inch) cake pans with nonstick baking spray and set them aside.

Using an electric handheld or standing mixer, beat the cake mix, butter, eggs, milk, and vanilla extract until combined and smooth.

Divide the batter evenly between the three prepared cake pans.

Bake in the oven for 25-30 minutes or until a toothpick inserted into the center of the cakes comes out clean.

Leave to cool for 5 minutes in the pan before turning out and transferring to a wire rack to cool completely.

When cool, use a knife or cake leveler to remove the dome from the cakes to create even layers.

To make the frosting, use an electric handheld or standing mixer to beat all of the frosting ingredients together until fluffy and creamy and can hold a peak.

Transfer 1 cup of frosting into a large piping bag fitted with an open star tip and set it aside.

To build the cake, place one of the cake layers onto a 10-inch cake board. You can smear a small blob of frosting onto the cake board to hold the cake in place.

Scoop 1½ cups of frosting on top of the first cake layer and smooth out evenly with a spatula.

Place the second layer of cake on top and scoop another 1½ cups of frosting and smooth evenly on top of this layer.

Place the third cake layer on top and frost the entire cake with the remaining frosting.

Sprinkle the chopped pistachios in a ring around the top layer of the cake as shown.

Using the piping bag of frosting, the pipe swirls around the inside of the pistachios.

Place the cake into the fridge for 1-2 hours to firm before slicing and serving. Enjoy!