In a medium bowl stir the sugar, flour and salt. Whip the egg yolks together then whisk them into the dry ingredients. This will create a thick "dough".
Place the milk into a small saucepan and scald it - the edges should start to bubble only. Pour it over the egg mixture, whisking all the time. When all the milk is whisked in, return to the pan and cook over medium-low heat until the mixture thickens. It will bubble, just keep whisking until the bubbles dissipate and the dough becomes more like pudding. This is your basic pastry cream.
Pour the pastry cream into a bowl, cover with plastic wrap and cool completely.
Preheat the oven to 350 and line two cookie sheets with silicon or parchment that has been slathered with butter.
In a large bowl, mix the coconut, egg whites, sugar, salt and cool pastry cream.
Use an ice cream scoop to measure out ¼ cup of the batter. You can leave the macaroons in domed shapes or for a more traditional look, shape into pyramids.
Bake for 25 - 35 minutes then let cool completely on the sheets.