Heat oven to 325ºF. Line a half sheet pan with parchment paper and set aside.
Combine the coconut with the sweetened condensed milk, salt, and vanilla in a medium mixing bowl.
In the bowl of a stand mixer fitted with the whisk attachment, beat the egg whites on medium speed until foamy. Gradually add the sugar and continue to whip the whites until medium peaks form, 6 to 7 minutes.
Gently fold the egg whites into the coconut mixture. Scoop tablespoon-sized mounds onto the prepared pan and bake until golden brown, 20 to 25 minutes. Immediately transfer the parchment with the macaroons to a cooling rack. Cool completely before topping.
Fill a 4-quart pot with enough water to come 2 inches up the side, set over medium heat, and bring to a simmer. Combine the chocolate chips and shortening in a small metal or glass mixing bowl and set over the simmering pot. Stir occasionally until melted, then remove from the heat.
Dip the cooled cookies in the chocolate mixture, sprinkle with the chopped macadamia nuts, and place on parchment paper to set, about 30 minutes.