In a bowl, sift together the cake flour, baking powder, baking soda, and salt.

In a large mixing bowl, cream the softened butter and sugar until light and fluffy.

Add the vegetable oil and mix until combined.

Add the eggs one at a time, beating well after each addition.

Add the dry ingredients in three additions, alternating with the milk and buttermilk. Begin and end with the dry ingredients.

Mix until just combined. Do not overmix.

Pour the batter into the prepared tin and smooth the top.

Bake for 25–30 minutes or until a skewer inserted into the centre comes out clean.

Allow the cake to cool completely, then refrigerate for at least 1 hour for easier cutting.

Cut into 12 equal squares.

Add the berries, sugar, and lemon juice to a saucepan.

Cook over medium heat until the berries soften and release their juices.

Mix the cornflour with a small amount of water to make a slurry.

Stir the slurry into the berry mixture.

Cook for 1–2 minutes until thickened.

Remove from the heat and allow to cool completely.

Place the chocolate dip mixture and water into a bowl.

Stir until smooth and pourable.

Place the raspberry dip mixture and water into a separate bowl.

Stir until smooth and pourable.

Dip each sponge square into either the chocolate dip or raspberry dip, coating all sides.

Allow any excess dip to drip off.

Roll each square in desiccated coconut until fully coated.

Place on a wire rack and allow the coating to set.

Pipe a swirl of fresh whipped cream onto the top of each lamington square.

Spoon or pipe a small amount of berry jam over the cream.

Serve immediately or refrigerate until needed.