• Prep and additional time depends on if you freeze the cake overnight or make everything same day. I suggest making the cake and the curd the first day, letting them chill overnight so making the icing and assembly is much quicker the next day. It took me about an hour to cut, fill, freeze, dip and roll all the cake squares.

Make the sponge cake:

• Heat oven to 325 Deg F
• Butter and line an 9x13 inch (or 8x12 inch) pan with parchment paper hanging over the long edges. 
• Whisk together the flour, corn starch and baking powder and salt in a small bowl. 
• Cream together the butter and sugar  then add in the eggs one at time, mixing well between each egg. Stop the mixer and scrape down the sides of the bowl when needed. 
• Mix together the passion fruit juice, milk and vanilla. Add this into the butter mixture alternating with the flour mixture until just combined. 
• Spread into prepared pan and smooth the top with a spatula. Bang the pan against your counter a few times to release air bubbles.  Bake for 20-25 minutes
• Cool in pan for 10 minutes then invert onto a wire rack to cool until still warm to the touch, keep the parchment paper on the cake.  Place the baking pan on the cake and flip back over so the cake is back in the pan. Wrap in plastic wrap then freeze completely, 3-4 hours up to overnight. 

Lamington assembly:

• When ready to make the Lamingtons, thaw the frozen cake slightly on a cutting board.
• While the cake is thawing make the sweetened cream. Whip the heavy cream and powdered sugar together until stiff.
• Trim off the edges of the cake and cut into two inch squares. Cut each square into two halves - top and bottom.  Spread a generous tablespoon of  curd on the bottom half, then spread a generous tablespoons of the sweetened cream on top of it then add the top half of the cake to make a mini sandwich. Repeat with all the squares.  Place on a parchment lined baking sheet and freeze again. 

Make the chocolate icing and finish the lamingtons:

• In a bowl set over a pan of water or a double boiler add the chopped chocolate and butter together and stir until melted then add the milk and whisk. In a separate bowl sift the powdered sugar and cocoa powder together. Whisk this in to the chocolate butter mixture and stir until smooth then transfer to a deep bowl. Add a cup and a half of the desiccated coconut in a wide shallow bowl. You will be changing out the coconut a few times as it gets sticky with chocolate icing.
• Working with one cake square at a time dip carefully in the chocolate to cover all sides, let excess drip off then quickly roll in the coconut to cover completely, pressing the coconut into the cake as you roll. Set the Lamington on a parchment lined baking tray and repeat with the remaining cake squares. 
• Serve immediately or chill and then thaw slightly before serving. Best served within a day or two of making.