Blackberry Olive Oil Cake with Mascarpone Frosting

Heat the oven to 175°C and line a 20cm (8") cake pan with parchment, greasing it with a little olive oil.

Rub the lemon zest into the sugar with your hands until fragrant.

Whisk in the olive oil, eggs and vanilla, then whisk in the sour cream and lemon juice.

In a separate bowl, whisk the flour with the baking powder, baking soda, salt and cornstarch, then fold this into the wet mixture just until combined.

Pour the batter into the pan and bake for 40 to 45 minutes, until a skewer comes out clean. Let the cake cool completely before assembling.

For the frosting, beat the mascarpone, cream, powdered sugar and vanilla together until smooth. Chill in the fridge until you're ready to assemble.

Cut 200g of the blackberries in half; leave the remaining 175g whole.

Once the cake is completely cool, slice it into two layers. Place the bottom layer on a board or plate, then spread over half the frosting and 2 tablespoons of jam. Scatter over 100g of the halved blackberries.

Set the second layer on top, then spread over the remaining frosting and 2 tablespoons of jam. Scatter over the rest of the halved blackberries, then pile the whole blackberries on top to finish.