Heat the oven to 180C/160C fan/gas 4. Tip the berries into a large saucepan with the jam, and heat gently for about 5 mins until just starting to turn saucy. Spoon some of the liquid into a small bowl and mix with the cornflour. Stir the cornflour mixture into the fruit mixture in the pan, and simmer for 2 mins. Pour into the base of a baking dish (ours was 18 x 25cm), then set aside.

Beat the butter and sugar together in a stand mixer, or using an electric whisk, for 5 mins until pale and fluffy. Add the eggs, one at a time, beating between each addition, then the vanilla, flour and peanut butter, beating briefly to combine. Stir in the milk to loosen the mixture. Carefully spoon the batter into the dish over the berries, then smooth the surface gently with the back of a spoon and scatter over the nuts. Bake for 45-50 mins. Leave to cool for 10 mins before serving warm with vanilla ice cream or custard.