Preheat the oven to 350°F (175°C) and line a 9x9-inch baking dish with parchment paper or heavy-duty aluminum foil, leaving a slight overhang for easy removal. Generously spray with nonstick cooking spray.
In a large mixing bowl, combine the all-purpose flour, unsweetened cocoa powder, and table salt. Whisk to combine.
In a 2 to 3-quart saucepan over medium heat, melt the sliced butter pats and chopped German chocolate baking bar, stirring until completely combined and melted. Remove from heat.
Stir in the light brown sugar and granulated sugar until well combined with the butter-chocolate mixture.
Add the eggs, one at a time, stirring well after each addition. Stir in the vanilla extract.
Add the butter and chocolate mixture to the flour mixture, stirring just until incorporated and no flour lumps remain. Fold in the semi-sweet chocolate chips.
Spread the brownie batter evenly into the prepared baking dish. Bake for 30-35 minutes, or until a toothpick inserted comes out with a few moist crumbs. Allow brownies to cool in the pan.
While brownies are cooling, make the coconut pecan frosting. In a 3 to 4-quart saucepan over medium heat, combine sliced butter, evaporated milk, light brown sugar, table salt, egg yolks, and vanilla extract. Stir continuously until the mixture thickens and turns golden caramel in color, about 9 to 10 minutes.
Stir in the sweetened coconut flakes and chopped pecans, and continue stirring until thickened, about 3-4 minutes. Spread the frosting evenly over the cooled brownies.
Use the parchment paper or foil overhang to lift the brownies out of the pan. Cut into squares. Optional: Melt chocolate melting wafers and drizzle over the frosting. Allow chocolate to solidify before serving.