01 - Preheat oven to 350°F. Grease an 8-inch square baking pan and line with parchment paper.
02 - In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
03 - In a large bowl, beat the softened butter and granulated sugar with an electric mixer until pale and fluffy. Add eggs one at a time, beating well after each addition. Stir in the vanilla extract.
04 - Gradually add the flour mixture to the butter mixture, alternating with the milk, mixing until just combined. Do not overmix.
05 - Pour the batter into the prepared pan and smooth the top. Bake for 20–25 minutes until a toothpick inserted in the center comes out clean.
06 - Let the cake cool completely in the pan, then turn out onto a wire rack. Wrap tightly and freeze for 30 minutes to firm up for easier dipping.
07 - Combine raspberries, water, sugar, and lemon juice in a saucepan. Simmer over medium heat for 5–7 minutes, stirring occasionally. Strain through a fine mesh sieve to remove seeds and let cool to room temperature.
08 - Using a serrated knife, cut the cooled sponge into 12 even squares.
09 - Spread desiccated coconut in a wide, shallow bowl. Dip each sponge square briefly in the cooled raspberry syrup, allowing excess to drip off, then roll in coconut to coat all sides evenly.
10 - For filled lamingtons, slice each square in half horizontally. Spread the bottom half with raspberry jam, pipe or spoon whipped cream on top, then sandwich with the upper half before dipping and coating.
11 - Place finished lamingtons on a wire rack to set for 15 minutes before serving.