Preheat the oven to 350 degrees.
Line a 9 x 9 baking pan with parchment paper.
Cream together the butter and brown sugar.
Add in the egg and vanilla and mix until well combined.
Add the flour, baking powder, salt, and shredded coconut. Mix until just combined.
Fold in the white chocolate chips.
Spread the batter into the prepared pan.
Bake for 17-20 minutes or until a toothpick inserted into the center comes out clean.
Remove from oven and cool completely.
In a large bowl beat the butter with a mixer on medium high speed until smooth.
Add in the powdered sugar, milk, and lime juice and beat for 2 minutes or until fluffy.
Add lime green coloring and mix until you achieve the color you are looking for.
Frost the cookie bars with all of the lime frosting.
If desired melt the white chocolate, put in a zip top baggie, snip the end, and drizzle over top of the bars. Quickly sprinkle with extra shredded coconut.
Allow the bars to sit for 15 minutes then cut into 16 bars and enjoy.