How to make:

1. Heat the unsalted butter until melted, then turn off the heat. Add the flour and stir until smooth and well combined. Remove from heat.

2. Pour the milk and lime juice into the egg yolks, then beat until well blended.

3. Gradually add this mixture to the butter–flour mixture while stirring until smooth. Set aside.

4. Beat the egg whites with salt and cream of tartar until half stiff. Gradually add the sugar while continuing to beat until the mixture is thick and glossy.

5. Pour the batter into a 26 × 26 × 4 cm baking pan. Sprinkle with desiccated grated coconut. Place the pan in a larger tray with a little water (au bain-marie method). Bake at 160°C (320°F) using bottom heat for about 50 minutes or until cooked through.

6. Remove from the oven and decorate with buttercream.

Yields 30 pieces.