Make the Brownies:

1. Preheat the oven to 350°F and line an 8-inch square baking dish with parchment paper. Whisk together the flour, salt, and baking soda in a small bowl; set aside.
2. In a medium saucepan over medium heat, melt the butter. Remove from heat and stir in the cocoa powder until smooth and glossy. Whisk in both sugars. Add the eggs and vanilla, stirring until fully incorporated. Switch to a wooden spoon and stir in the dry ingredients.
3. Pour batter into the prepared pan and bake 25–28 minutes. Remove and let cool completely.

Make the Frosting:

1. In a medium saucepan, whisk together the egg yolks and evaporated milk. Stir in the brown sugar, butter pieces, and salt.
2. Cook over medium heat, stirring constantly, until the mixture comes to a boil and thickens, about 10–12 minutes. The frosting is ready when it coats the back of a spoon and leaves a clean line when you run your finger through it.
3. Remove from heat and stir in the vanilla, shredded coconut, and chopped pecans. Let cool to room temperature, stirring occasionally — it will thicken further as it cools.

Assemble:

1. Once both the brownies and frosting have cooled to room temperature, spread the frosting evenly over the brownies. Refrigerate for at least 1 hour, or until the frosting is fully set, before cutting.