Preheat oven to 350 F. Line baking sheets with parchment paper or silicone baking mats. Set aside.
Add the melted butter and brown sugar to a large mixing bowl, and whisk until well-combined.
Whisk in the egg, egg yolk, and vanilla until well-combined.
Add the flour, baking powder, baking soda, and salt. Whisk in until just combined.
Whisk in the oats just until incorporated.
Add the baking chocolate, pecans, and coconut, and whisk in until combined.
Drop by 1.5 tablespoon scoops (medium cookie scoops) 2 inches apart on prepared baking sheet.
Bake 8-14 minutes. The cookies should be light golden brown at the edges but look underdone in the middle. This will help to keep them soft and chewy.⁵
Video
Notes
I recommend melting the butter most of the way and then whisking to finish melting the butter. It takes about 40 seconds in my microwave.
Be sure to either weigh or sift or stir the flour, lightly spoon into the measuring cup, and then level to avoid packing in the flour.
Or 1/4 teaspoon table salt.
Or 12 ounces semisweet chocolate chips
Overbaking the cookies will give you a crunchier cookie.