01 -
Preheat oven to 175°C and lightly grease a 33 x 46 cm sheet pan.
02 -
Combine 227 g unsalted butter and 240 ml water in a medium saucepan; bring to a boil, then remove from heat.
03 -
In a large bowl, whisk together 400 g granulated sugar, 250 g all-purpose flour, 0.5 teaspoon salt, and 1 teaspoon baking soda.
04 -
Pour hot butter-water mixture over dry ingredients and stir until thoroughly combined.
05 -
Add 2 large eggs, 120 g sour cream, and 1 teaspoon vanilla extract; mix until batter is smooth and homogenous.
06 -
Fold in 70 g sweetened shredded coconut until evenly distributed.
07 -
Evenly spread batter into the prepared sheet pan and bake for 18–20 minutes, or until a toothpick inserted in the center emerges clean.
08 -
While the cake bakes, melt 113 g unsalted butter with 60 ml milk in a medium saucepan over medium heat.
09 -
Remove pan from heat; gradually whisk in 360 g powdered sugar and 1 teaspoon vanilla extract until smooth.
10 -
Fold in 70 g sweetened shredded coconut to the frosting.
11 -
When cake is baked, let it cool briefly, then spread frosting evenly over the warm surface.
12 -
Allow cake to cool completely before cutting into squares for serving.