Make the cookies: Preheat the oven to 325 degrees F. Line 2 baking sheets with parchment paper. Lightly beat the egg whites in a medium bowl until frothy, then stir in the granulated sugar, almonds, vanilla and salt. Fold in the coconut.
Drop tablespoonfuls of the batter 1 inch apart on the prepared baking sheets. Dampen your hands and form into tall pointed mounds. Bake until the edges are golden brown and the macaroons look dry, 16 to 20 minutes. Let cool 10 minutes on the baking sheets, then transfer to a rack to cool completely.
Make the glaze: Put the chocolate, corn syrup, butter and 3 tablespoons hot water in a microwave-safe bowl. Cover with plastic wrap and microwave until melted, about 2 minutes. Whisk until smooth.
Dip the tip of each macaroon about halfway into the glaze, then place on a clean parchment paper-lined baking sheet. Sprinkle with coarse sugar, then refrigerate until the glaze sets, about 1 hour. Store in an airtight container up to 1 week.