Preheat the oven to 180C/160C Fan/Gas 4. Grease and line two 20cm/8in sandwich tins: use a piece of baking or silicone paper to rub a little baking spread or butter around the inside of the tins until the sides and base are lightly coated. Line the bottom of the tins with a circle of baking paper.

Break the eggs into a large mixing bowl, add the sugar, flour, baking powder and soft butter. Mix everything together until well combined. Be careful not to over-mix – as soon as everything is blended you should stop. The finished mixture should be of a soft ‘dropping’ consistency.

Divide the mixture evenly between the tins. Use a spatula to remove all of the mixture from the bowl and gently smooth the surface of the cakes.

Place the tins on the middle shelf of the oven and bake for 25 minutes. Don’t be tempted to open the door while they’re cooking, but after 20 minutes do look through the door to check them.

While the cakes are cooking, make the jam. Put the raspberries in a small deep-sided saucepan and crush them with a masher. Add the sugar and bring to the boil over a low heat until the sugar has melted. Increase the heat and boil for 4 minutes. Remove from the heat and carefully pour into a shallow container. Leave to cool and set.

The cakes are done when they’re golden-brown and coming away from the edge of the tins. Press them gently to check – they should be springy to the touch. Remove them from the oven and set aside to cool in the tins for 5 minutes. Then run a palette or rounded butter knife around the inside edge of the tin and carefully turn the cakes out onto a cooling rack.

To take your cakes out of the tins without leaving a wire rack mark on the top, put the clean tea towel over the tin, put your hand onto the tea towel and turn the tin upside-down. The cake should come out onto your hand and the tea towel – then you can turn it from your hand onto the wire rack. Set aside to cool completely.

For the buttercream, beat the butter in a large bowl until soft. Add half of the icing sugar and beat until smooth. Add the remaining icing sugar and one tablespoon of the milk and beat the mixture until creamy and smooth. Add the remaining tablespoon of milk if the buttercream is too thick. Spoon the buttercream into a piping bag fitted with a plain nozzle.

To assemble, choose the sponge with the best top, then put the other cake top-down on to a serving plate. Spread with the jam then pipe the buttercream on top of the jam. Place the other sponge on top (top uppermost) and sprinkle with caster sugar to serve.