This is a classic school dinner dessert that many of us Brits have loved with a passion: warm soft sponge smeared with delicious sour jam and covered in coconut. A little slice of this is brilliant with a pot of tea for a midday treat, or as a dessert with a splodge of hot or cold custard. Just pure nostalgia through and through.
Grease and line the bottom of a 30 x 20cm cake tin. Preheat the oven to 180°C/350°F/gas 4.
Cream the butter and sugar together until lovely, pale and fluffy, then beat in the eggs, one at a time. Fold in the flour and baking powder, add a splash of milk and the vanilla extract, and mix again. Pour into the lined tin and cook in the oven for 25 to 30 minutes. While your cake is cooking, get on with making the blackberry jam.
Mash the blackberries and sugar together in a small pan, using a fork or a potato masher, then add a squeeze of lemon juice and bring everything to the boil. Turn down to a medium heat and simmer for about 20 minutes, stirring occasionally, until lovely and thick. Skim away any foam that rises as the jam cooks, then take off the heat and leave to cool slightly.
By now, the sponge should be golden and cooked through, so remove it from the oven and leave to cool for 5 to 10 minutes. Turn it out on to a board, then pour the jam all over the sponge and use a palette knife to move it all around the sponge and the sides. Sprinkle over the desiccated coconut and serve.