BUTTER AND SUGARS: In the bowl of a stand mixer fitted with the whisk attachment (or use a large bowl and a hand mixer), add the room temperature butter (not melted, not softened) and dark brown sugar. Beat at medium speed until light in color, about 1-2 minutes. Add in the egg and vanilla and beat until light and fluffy, about 2 more minutes. Scrape down the sides of the bowl as needed.
BAKING AGENTS: Add in the baking soda and fine sea salt. Mix until just combined, about 20 seconds.
FLOUR, OATS, AND COCONUT: Add in the oats, flour, and coconut. Mix until just combined, about 30 seconds.
CHOCOLATE CHIPS: Add in the chocolate chips and mix until ingredients are JUST combined. Do not overmix or overbeat. Overworking the dough will result in dense cookies.
SHAPE TALL COOKIE BALLS: Shape the cookie dough into balls about 2 and 1/2 tablespoons of dough (if you have a food scale: 49 grams; 1.7 ounces). Roll the balls higher instead of wider (see photo in post). Place them on a plate lined with parchment paper and cover gently with plastic wrap. Refrigerate at least 30 minutes and preferably 45 minutes to an hour. If you're in a rush, freeze the dough balls for about 25-30 minutes.
BAKE: Preheat oven to 350 degrees F. Line 2 half-sheet pans with Silpat liners (very important that the trays are lined, so the cookies don't burn on the bottom). Place 6 cookie dough balls per sheet pan (they spread a lot!), spacing them with plenty of room to spread. Bake for 9 to 13 minutes (mine always take around 11 minutes), remembering they're best slightly under-baked. They should look ever-so-slightly gooey in the center (they harden a bit as they cool) and should be lightly browned around the edges. Remove from the oven and let stand on the cookie sheet for 5-10 more minutes to firm up enough to remove to a wire cooling rack. Right out of the oven you can press a few more chocolate chips in the tops of the cookies if desired (makes them look better and ensures chocolate in every bite!).
COOL AND ENJOY: Let cookies fully cool and set up before eating; they firm up a lot as they cool! Store in an airtight container at room temperature for up to 4 days. Cookies are best when eaten within 2-3 days.