Preheat your oven to 350 degrees F (175 degrees C). Lightly grease and flour a 9×13 inch baking pan, or line with parchment paper leaving an overhang for easy removal.

In a large bowl, whisk together the melted butter and granulated sugar until well combined.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract. Continue mixing just until the batter is smooth and glossy.

In a separate bowl, whisk together the flour, cocoa powder, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed or by hand just until no streaks of flour remain. If using, fold in the 1/2 cup chopped pecans.

Pour the brownie batter into the prepared baking pan and spread evenly.

Bake for 25 to 30 minutes, or until a toothpick inserted into the center comes out with moist crumbs, not wet batter.

While the brownies are cooling, prepare the topping. In a medium saucepan, combine the coconut, 1/2 cup chopped pecans, evaporated milk, 1/2 cup granulated sugar, butter, and egg yolk.

Cook over medium heat, stirring constantly, until the mixture thickens and comes to a boil. Reduce heat to low and continue stirring for 3-5 minutes, until it's very thick.

Remove from heat and stir in the vanilla extract. Pour the warm topping evenly over the cooled brownies.

Let the brownies cool completely at room temperature or chill in the refrigerator for at least 2 hours before cutting into squares.