Fit a stand mixer with the whisk attachment. Add the egg whites to a clean, completely dry bowl and beat on low speed, gradually increasing to high, until glossy, stiff peaks form. The whites should stand straight when the whisk is lifted without drooping.
In a separate small bowl, whisk together the caramel sauce, sweetened condensed milk, flour, and vanilla until smooth and fully combined.
Using a rubber spatula, gently fold the caramel mixture into the whipped egg whites, scraping down the sides of the bowl and folding from the bottom up. Continue just until no streaks of egg white remain, taking care not to deflate the mixture.
Fold in the shredded coconut until evenly distributed.
Use a 2-ounce cookie scoop to portion the batter onto a parchment-lined baking sheet, spacing the macaroons about 2 inches apart.
Bake at 325°F for 12–14 minutes, until the tops are lightly golden, the coconut flakes are toasted, and the centers feel set.
Drizzle the tops or dip the bottoms with melted chocolate.