Preheat the oven to 325°F. Line an 8×8-inch baking dish with parchment paper and lightly spray with nonstick baking spray.
Separate the eggs, placing the yolks in a large mixing bowl and the whites in a separate clean bowl.
Beat the egg whites with a hand mixer on medium-high speed until stiff peaks form. Set aside.
Add the granulated sugar to the egg yolks and beat for two to three minutes, until pale and slightly thick.
Pour in the melted butter and beat until smooth.
Add the flour and salt. Mix on low speed until combined.
Slowly pour in the coconut milk and warm whole milk while mixing on low speed. Add the vanilla extract and coconut extract, if using.
Gently fold the whipped egg whites into the batter in three additions. The batter should look thin and slightly lumpy from the egg whites.
Fold in the sweetened shredded coconut.
Pour the batter into the prepared baking dish.
Bake for 55 to 65 minutes, or until the top is golden and the center has a slight jiggle.
Cool completely at room temperature, then cover and refrigerate for at least two hours.
Dust with powdered sugar and garnish with toasted coconut before slicing and serving.