Preheat your oven to 350 degrees F (175 degrees C) and line a baking sheet with parchment paper.

In the bowl of a stand mixer, combine the room temperature butter, granulated sugar, and confectioners' sugar. Mix until just combined—no need for it to be airy!

Drizzle in the vegetable oil, and add the eggs, water, and vanilla extract. Mix until the mixture is smooth and well combined.

In another bowl, whisk together the all-purpose flour, Dutch-process cocoa, kosher salt, baking soda, and cream of tartar. This will help evenly distribute the dry ingredients.

Gradually add the flour mixture into the butter mixture. Mix on low speed until the dough begins pulling away from the sides of the bowl.

Gently fold in the sweetened coconut until well incorporated.

Use a 2-tablespoon scoop to drop dough onto the prepared baking sheet. Flatten each ball slightly with a glass dusted with sugar.

Bake in the preheated oven for 7-8 minutes. The edges should be set, and they may look slightly underbaked in the center—the cookies will continue to cook as they cool.

While the cookies cool, combine sweetened condensed milk, brown sugar, and butter in a saucepan over medium heat. Stir frequently until thickened (about 10 minutes).

Once thickened, remove it from heat. Stir in vanilla, pecans, and sweetened shredded coconut.

Once the cookies are cool, generously spoon about a tablespoon of the coconut-pecan frosting on each cookie.