Blackberry and Pistachio Crumble Cake with Pistachio Custard

Heat the oven to 180C/160C fan/gas 4. Grease and line a 20cm square cake tin.

Beat the softened butter, oil and caster sugar until pale. Beat in the eggs one at a time, then mix in the vanilla.

Fold in the flour, ground almonds, baking powder and salt. Spread the batter into the tin and scatter over the blackberries.

Mix the chopped pistachios with a little butter, flour and sugar to make a rough crumble, then scatter it over the fruit.

Bake for 45–55 minutes, until golden and a skewer inserted in the centre comes out clean. Cool in the tin before slicing.

For the custard, warm the milk and cream with the sugar. Whisk the egg yolks and pistachio paste in a bowl, then gradually whisk in the hot dairy.

Return the custard to the pan and stir over low heat until it lightly coats the back of a spoon; do not let it boil.

Serve the cake with the pistachio custard and finish with a dusting of icing sugar.