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)
Make the sponge by mixing the butter (or baking spread) and caster sugar together in a mixing bowl until fluffy (around 3 minutes), ideally using an electric mixer
Add the eggs and vanilla extract, and whisk until fully incorporated
Add the self raising flour and mix or fold in gently until you can't see any flour anymore
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 on it's own until it's smooth and creamy. Use an electric mixer with the paddle attachment for best results
Add the icing sugar, vanilla extract and milk. Mix until smooth. If the buttercream is too stiff then you can add a little more milk
If the cakes have domed on top, level them off with a cake leveller or a sharp knife
Put one of the sponges on your plate or cake stand and pipe or spread some of the buttercream onto it
Add the other sponge on top and pipe or spread the remaining buttercream on top
Decorate with your choice of chocolates, sweets, sprinkles or fresh fruit
Leftovers will keep in an airtight container in a cool place for 3 days
Video
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.
You can decorate this cake with anything you like! If it is for someone's birthday, perhaps their favourite chocolates on top. Fresh strawberries or raspberries would also look fabulous!
I recommend using a good quality vanilla extract and/or paste, and not an essence. Extract is real vanilla, whereas essence is synthetic.
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.