Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and grease and line two 8" cake tins (that are at least 2" deep)
For the sponge, mix together the baking spread (or butter) and caster sugar, ideally using an electric hand mixer or in a stand mixer with the paddle attachment, for around 3 minutes until smooth and fluffy
Add the eggs and mix them in well
Grind the pistachios in a high speed blender or food processor. Gently whisk, or fold in, the self raising flour, ground pistachios and baking powder
Divide the mixture between the tins, use scales for accuracy if you like. Bake them for 35-40 minutes or until a thin skewer inserted in the middle comes out clean. Leave them to fully cool either in the tins or remove from the tin and place on cooling racks
To make the buttercream, mix the butter for a few minutes on it's own. Add the pistachio cream spread, icing sugar and milk, and mix until smooth. You can add a little more milk if the buttercream is too stiff. Use an electric mixer for the best results
If the cakes have domed on top, level them off with a cake leveller or a sharp knife. Place one of the sponges on your plate or cake stand. Put the buttercream into a large piping bag fitted with a nozzle of your choice and pipe (or spread if not using a piping bag) some of the buttercream onto it
Add the other sponge on top and pipe or spread the remaining buttercream on top
Warm the pistachio spread in the microwave for 10-20 seconds and drizzle it over the cake. Decorate with the chopped pistachios
Store in an airtight container in a cool place and eat within 3 days
Notes
Make sure all your ingredients (particularly the butter and eggs) are at room temperature before you start baking.
I used a baking spread for the cake and unsalted butter for the buttercream.
Although I provide cup measurements, I highly recommend weighing your ingredients out using digital kitchen scales. It is the most accurate way to measure ingredients and will ensure the best results. Digital scales are very low cost and can be purchased for around £12 ($16.50).
For teaspoon (tsp) and tablespoon (tbsp) measurements, please use measuring spoons and not the type of spoons you eat with. Again this will ensure accuracy and provide the best results.