Makes 45 to 50 cookies
Preheat the oven to 200 degrees. Position racks in the upper and lower thirds of the oven
Set aside and mix together 1/4 of the macadamia nuts, dark chocolate chunks, and coconut for the topping.
Mix the remaining nuts, dark chocolate chunks, and coconut with the milk chocolate pieces and 2 tablespoons of the sugar. Set aside.
Combine the egg whites and cream of tartar in a clean dry bowl. Beat at medium-high speed with a heavy-duty stand mixer (or high speed with a hand mixer) until the egg whites are creamy white (instead of translucent) and hold a soft shape when the beaters are lifted. Continue to beat on medium to high speed, adding the remaining sugar a little at a time, taking 1 1/2 to 2 minutes in all, until the egg whites are very stiff and have a dull sheen. Pour the mixture of nuts, coconut, both chocolates, and sugar over the meringue and use a large rubber spatula to fold them in, just until blended.
Drop generous tablespoons of meringue 1 1/2 inches apart on the lined cookie sheets. Make sure all of the batter fits on the two sheets so all can be baked at once; if necessary make each cookie a little bigger. Top the meringues with a pinch of the reserved topping mixture. Bake for 1 1/2 hours, rotating the pans from top to bottom and from front to back halfway through the baking time to ensure even baking. Remove a test meringue and let it cool completely before taking a bite (meringues are never crisp when hot). If the test meringue is completely dry and crisp, turn off the oven and let the remaining meringues cool completely in the oven. If the test meringue is soft or chewy or sticks to your teeth, bake for another 15 to 30 minutes before cooling in the oven.
To prevent cookies from becoming moist and sticky, put them in an airtight container as soon as they are cool. Cookies keep for at least 2 weeks.