01 - Preheat your oven to 350°F (175°C). Line a 9x13-inch (23x33 cm) baking pan with parchment paper, ensuring there's an overhang for easy removal.
02 - Cream the softened butter and granulated sugar in a mixing bowl until light and fluffy. Incorporate the all-purpose flour and salt until just combined. Press the dough evenly into the prepared baking pan. Bake for 18–20 minutes, or until the edges are lightly golden. Allow to cool slightly.
03 - In a saucepan, whisk together granulated sugar, cornstarch, and salt. Gradually whisk in the whole milk and coconut milk until a smooth mixture forms. Cook over medium heat, whisking constantly, until the mixture thickens and comes to a boil, approximately 5–7 minutes.
04 - In a separate bowl, whisk the egg yolks. Slowly pour about 1/2 cup of the hot milk mixture into the yolks while whisking constantly to temper them. Return the tempered egg mixture to the saucepan, continuing to whisk vigorously. Cook for an additional 2 minutes, then remove from heat.
05 - Stir in the butter, vanilla extract, and shredded coconut into the warm filling. Pour the filling over the cooled shortbread crust and smooth the surface. Allow to cool at room temperature for 30 minutes, then refrigerate for at least 1 hour, until adequately set.
06 - In a chilled mixing bowl, beat the cold heavy whipping cream, powdered sugar, and vanilla extract until stiff peaks form. Spread this whipped cream mixture evenly over the chilled coconut custard.
07 - Garnish the bars with the toasted shredded coconut. Cut into desired bar portions and serve chilled.