Heat oven to 250 degrees F. Spread the coconut evenly on a baking sheet, transfer to the oven and bake until just golden, about 10 minutes. Set aside to cool.
Place butter, coconut and sugars in the bowl of a mixer fitted with a paddle and beat until smooth and creamy. Scrape down side of bowl, add the flour and salt, beat well and scrape again. Form the dough into a 1 1/2-inch-diameter log and cover with parchment
paper. Place the log in a resealable plastic bag and refrigerate at least 1 hour and up to 2 days, or freeze up to 2 months.
Heat oven to 325 degrees F.
With the tip of a very sharp knife, cut 1/4- to 1/2-inch slices of the dough and place 2 inches apart on prepared pan. Transfer to oven and bake until cookies are just beginning to brown on the edges, about 20 minutes. Transfer to a wire rack to cool. Let the cookie sheet cool completely between batches and repeat with the remaining dough.