Preheat oven to 350F. Line an 8-by-8-inch baking pan with aluminum foil, spray with cooking spray; set aside.
In a large, microwave-safe bowl melt the butter, about 1 minute on high power.
Wait momentarily before adding the egg so you don’t scramble it. Add the egg, brown sugar, lime juice (I used closer to 1/3 cup), lime zest, vanilla, and whisk until combined.
Add the coconut and stir to combine.
Add the flour, optional salt, and stir until just combined; don’t overmix.
Add the white chocolate chips and stir to combine.
Turn batter out into prepared pan, smoothing the top lightly with a spatula.
Bake for about 30 minutes, or until a toothpick inserted in the center comes out mostly clean, or with a few moist crumbs, but no batter.
Allow bars to cool in pan for about 30 minutes before glazing.
In a medium bowl, add confectioners’ sugar, lime juice, and whisk until smooth. As necessary, add additional lime juice (or sugar) to reach desired glaze consistency. Glaze should be fairly thin and easily pourable over the bars.
Evenly pour glaze over bars, smoothing it lightly with a spatula as necessary.
Evenly sprinkle about coconut over the top before slicing and serving.
