1. Preheat the oven to 190ºC (375ºF, gas mark 5). Grease and baseline two 20.5cm (8in) sandwich tins. Beat the butter and sugar until pale and light. Gradually beat in the eggs.
2. Sift the flour over the cake batter and fold in gently. Divide the mixture evenly between the tins and level with a knife. Bake in the oven for 20-30 mins or until well risen, firm to the touch and shrinking away from the sides of the tin. Turn out and leave to cool on a wire rack.
3. Cut each cake in half horizontally. Make the butter icing by beating the butter in a large bowl until soft. Add half the icing sugar and beat until smooth, then add the remaining icing sugar with 1tbsp milk and the vanilla extract. Beat until creamy. Add icing sugar to thicken or milk to make runnier, as necessary. Sandwich the cake halves together with the butter icing (so you still have two separate cakes).
4. Place one of the cakes on a plate, spread with the jam and set the other cake on top. Dust with icing sugar and decorate with fresh summer berries.

Nutritional information

Guideline Daily Amount for 2,000 calories per day are: 70g fat, 20g saturated fat, 90g sugar, 6g salt.