This is a recipe with a cool trick. I took another recipe that I loved (Flo Braker's Pains D'amande http://food52.com/recipes...), one of my favorites, and changed the flavor profile to coconut and lime. By experimenting with the recipe, I found that by not letting the mixture come to a boil, and by adding the turbinado sugar just before the dry ingredients, the sugar stays crunchy, which helps contribute to the crispy texture of the cookies.
Whisk the flour, salt and baking soda together in a small bowl; set aside.
In a 1 1/2-quart saucepan over low heat, combine the butter, coconut chips and lime juice/rum (or water) mixture. Stir occasionally just until the butter melts. Do not allow the mixture to boil. Pour this mixture into a 3-quart mixing bowl; set aside for about 30 minutes at room temperature until lukewarm.
Stir in the sugar, then add the lime zest (use all of it), and the rest of the dry ingredients all at once; fold until completely blended.
Pack the soft dough firmly into a loaf pan lined with plastic wrap. Cover surface with plastic wrap and refrigerate or freeze until firm.
Place a rack in the lower third of oven and heat oven to 325 degrees F. Line two large baking sheets with parchment paper.
Lift the dough from the pan and place onto a cutting board. Cut the dough in thirds crosswise. With a very sharp knife, cut each bar into 1/8-inch or thinner slices, and space them 1/4 inch apart on the baking sheets.
Bake, one sheet at a time, for 8 to 10 minutes, or until the undersides are light golden; then rotate cookie sheets 180 degrees and bake for an additional 8 to 10 minutes, or until crisp and honey-colored. Place baking sheet on a wire rack to cool completely before removing cookies. (The dough freezes well if you only want to make a half or third batch.)