Line a large baking sheet with parchment paper and set aside.
First, start by toasting your coconut flakes. Add coconut flakes to a large skillet and set over medium-low heat. Cook the coconut for 3-5 minutes stirring constantly until the coconut is golden brown. Set the coconut flakes aside to cool.
While the coconut is cooling, add dark brown sugar, cocoa powder, unsalted butter, milk, and a pinch of salt in a medium-sized saucepan.
Cook, stirring until the sugar is dissolved and the mixture starts to boil. Remove from the heat and stir in vanilla.
Add quick-cooking oats, toasted coconut, and chopped peanuts. Stir until well combined.
While the mixture is still warm, drop the cookies by a rounded tablespoon onto the prepared baking sheet.
Place the cookies in the refrigerator for 30 minutes before serving.
Notes
For this recipe you can use quick cooking oats, but not instant oats. The instant oats will give you very fine and almost mushy cookies. You can also try the regular rolled oats, but haystack cookies made with rolled oats will be chewier. The quick-cooking oats are a perfect cross of these two, as they will absorb moisture at a moderate rate, maintaining their shape better, but with a little less chewiness classic rolled oats have.