Step 1: Prepare the Cake Batter: In a large mixing bowl, combine the yellow cake mix, coconut milk, vegetable oil, eggs, and coconut extract. Blend using an electric mixer until smooth and well combined, ensuring no lumps remain. The batter will be slightly thinner than a traditional cake batter, which is expected due to the coconut milk.
Step 2: Bake the Cake: Grease and flour a 9x13 inch baking pan. Pour the cake batter into the prepared pan, spreading it evenly. Sprinkle half of the shredded coconut (3/4 cup) evenly over the batter.
Step 3: Bake: Bake in preheated oven at 350F (175C) for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean. Monitor the cake carefully to prevent over-browning, as baking times may vary depending on the oven.
Step 4: Prepare the Coconut Milk Mixture: While the cake is baking, prepare the mixture to soak the cake. In a bowl, whisk together sweetened condensed milk and remaining coconut milk.
Step 5: Soak the Cake: Once the cake is out of the oven, immediately poke holes all over it using a fork or skewer. Pour the sweetened condensed milk mixture evenly over the cake, allowing it to soak in. The mixture should cover the entire surface of the cake.
Step 6: Top and Cool: Sprinkle the remaining shredded coconut (3/4 cup) over the top of the soaked cake. Let the cake cool completely in the pan before cutting and serving. Refrigerate for at least 2 hours for best flavour, and to allow milk to settle in the cake.
Optional Tips: For a toasted coconut flavour, toast the shredded coconut in a dry skillet over medium heat until golden brown, stirring constantly to prevent burning. Substitute almond extract for coconut extract to change the taste.