• Preheat the oven to 340F (170C). Grease and line with parchment paper a 9x13 cm (23x33 cm) pan.

Prepare the vanilla sponge cake.

• Separate whites from yolks.
  
• In a medium bowl mix yolks with ½ cup (100g) sugar and vanilla extract, until creamy and pale yellow colored.
  
• Gradually mix in oil and then add milk.
  
• In a large bowl, mix egg whites with salt until foamy.
  
• Gradually add the remaining ½ cup sugar. Continue mixing until soft peaks form.
  
• Gently fold the yolk mixture into the whipped whites.
  
• Gradually sift the flour and baking powder over the egg mixture.
  
• Gently fold them in.
  
• Pour the batter into the prepared pan.
  
• Bake for 20-25 minutes, until a toothpick inserted into the center comes out clean.
  
• Let it cool for about 10 minutes. Remove from the pan and cool completely on a rack.

Prepare the chocolate sauce.

• In a small saucepan add sugar and cocoa powder. Stir to combine and gradually add water, while stirring to combine well.
  
• Add the butter and place over medium heat. Bring to a boil and simmer over low heat for about 4-5 minutes, stirring constantly.
  
• Remove from heat and add vanilla or rum extract and semisweet chocolate chips.
  
• Stir until the chocolate is melted.

Prepare the lamingtons.

• Trim the edges of the sponge cake. Cut into 2-inch (5cm) squares.
  
• Place about 1 cup of desiccated unsweetened coconut into a bowl.
  
• Dip each square of sponge cake into the chocolate sauce, you can use a fork to make it easier.
  
• Coat each lamington in coconut and transfer to a serving plate.
  
• Repeat with the remaining sponge cake squares.
• Gradually, add more coconut in the bowl, as needed, for coating the lamingtons.
• Refrigerate for about 1 hour before serving. Enjoy!