1. Preheat oven to 190c or gas mark 5. Simply blitz all of the cake ingredients together in the food processor except the milk which you drizzle in last through the funnel before pulsing a few times to a smooth batter.
2. Spoon the mixture into large muffin cases in a 12 hole muffin tray so that they are around two thirds full. Bake for around 15-18 minutes. For 12 large cupcakes I set the timer for 12 minutes, turn around and leave for another 6 minutes. For standard cupcake size and mini muffin size I set the timer for 10 minutes, turn around then give them a further
3. The centres may erupt like little volcanoes but that’s ok, you can lop off these peaks if you want to ice them flat. Or, I have found lately that cooking them on a lower oven shelf seems to stop the eruption but your oven may behave differently.
4. When they are done a cocktail stick will just about come out dry. With practice you get the confidence to know how early this is, leaving them even a couple of minutes beyond this point will make your sponge too dry.
5. Leave to cool in the tins for a few minutes before transferring to a wire rack. Allow to cool completely before covering with icing.
6. For the buttercream, tip the softened butter, sifted icing sugar, lemon and milk into the food processor and mix until fully mixed and very soft and fluffy. Add another tablespoon of milk if you think it’s still too stiff. Beat the buttercream with the mixer for up to a minute, it will go fluffier and lighter. Remember that although it will be soft and squidgy now, the surface of the buttercream will go harder when it’s had a couple of hours to dry out on the surface of a cake. If it lasts that long.
7. Paste your buttercream over the cool cupcake bases using a small palette knife.
8. If colouring your buttercream, you can either add this in the food processor or if you want lots of different colours, divide your icing into as many bowls you would like colours. Dip a cocktail stick into your gel food colouring and swirl around in the buttercream. Mix thoroughly with a small palette knife. Add further food colouring with a clean cocktail stick for a deeper colour.