Preheat oven to 325° F.: As the oven warms, you will notice a dry, warming smell that helps when you first test a rack placement. Ensuring the oven reaches the correct heat is key for even browning and the right texture. If the oven is cooler than indicated, the macaroons will dry out before they brown; use an oven thermometer if you suspect your range runs cool.
Line two baking sheets with parchment paper and set aside.: The parchment creates a nonstick surface so the macaroons release cleanly and the bottoms do not overbake into a dark, hard layer. Run your fingers along the sheet to smooth any wrinkles, because an uneven surface can make the cookies bake unevenly. Do not skip parchment, or the macaroons may stick and break when you try to transfer them.
In a large bowl, stir together coconut, sweetened condensed milk, and vanilla. Then stir in the pecans and chocolate chips. Sprinkle the flour over the coconut mixture and fold to incorporate.: At this stage you will smell the sweetened condensed milk mingling with vanilla , and the coconut should begin to stick together into a cohesive mass. This step hydrates the coconut and creates the base texture. If the mixture looks too dry, allow it a few minutes for the coconut to absorb liquid; adding more condensed milk will change sweetness and consistency.
In the bowl of a stand mixer fitted with the whisk attachment, whip the egg whites and salt on high speed until there are medium-firm peaks. Very gently fold the whipped egg whites into the coconut mixture.: When you add the chopped pecans and mini chocolate chips , fold gently until evenly distributed, listening for the faint clink of chips settling. This creates pockets of flavor without overworking the base. Overmixing here can bruise the texture and break up chips into crumbs, which reduces the delightful chocolate pockets.
Using a 2" diameter cookie scoop, pack the coconut mixture fairly tightly, and drop the batter onto prepared baking pans. Bake for about 35 minutes, or until golden brown, alternating pans halfway through baking if baking both pans at the same time.: The small dusting of flour absorbs a bit of moisture and firms the mixture so the scooped mounds keep their shape. You should see the batter become slightly less glossy, and it should cling together when pressed. Be careful to fold lightly; aggressive mixing will make the batter tough and can flatten the macaroons when baked.
Cool on the pan for 5 minutes and then remove macaroons to a cooling rack.: As you whip, the whites will transform from clear to glossy white, and you will hear a thicker, more elastic sound as peaks form. Medium-firm peaks will hold shape but still have a slight bend at the tip, which gives structure without dryness. A common mistake is underwhipping, which yields slack whites and dense macaroons, or overwhipping, which makes them dry and prone to cracking.
Very gently fold the whipped egg whites into the coconut mixture.: When folding, you will notice the batter lighten visually and become airier. Use a large spatula and scoop from the bottom up, turning the bowl as you go to keep as much volume as possible. The sound will be quieter, and the mixture will look less glossy, signaling even distribution. If you stir too vigorously you will deflate the whites, producing heavy, dense cookies.
Using a 2" diameter cookie scoop, pack the coconut mixture fairly tightly, and drop the batter onto prepared baking pans.: As you scoop, you should see neat, domed mounds that hold together. Packing the scoop ensures the macaroons do not crumble when transferred, and the domed top gives a pretty, rustic silhouette after baking. If the mounds spread during baking, it usually means they were not packed enough or the oven was too warm.
Bake for about 35 minutes, or until golden brown, alternating pans halfway through baking if baking both pans at the same time.: During baking the kitchen will fill with a toasty coconut aroma and you will see the edges take on a warm golden color while the centers remain slightly paler and tender. Rotating the pans evens out hot spots so colors match. Remove them too soon and the centers will be gummy, bake too long and they will harden and lose chew.
Cool on the pan for 5 minutes and then remove macaroons to a cooling rack.: Cooling briefly on the sheet lets the bottoms set, and transferring them to a rack stops carryover baking so the centers remain chewy. You will feel a slight firming when you touch the base after a few minutes. If you try to move them immediately while very hot they may fall apart, so patience here preserves shape.