Preheat the oven to 350°F, line a nine by thirteen inch pan with parchment paper, and lightly grease it.
Melt the butter and chopped chocolate over low heat until smooth, then let cool briefly.
Whisk in granulated sugar and brown sugar, add eggs one at a time, then stir in vanilla.
Whisk flour, cocoa powder, and salt, then gently fold into the batter just until combined.
Spread the batter in the pan and bake for 22 to 28 minutes, until set with moist crumbs. Cool completely.
Cook evaporated milk, egg yolks, sugar, and butter over medium heat until thickened, about 8 to 12 minutes.
Stir in vanilla, shredded coconut, and chopped pecans, then let the topping cool slightly.
Spread the topping over the brownies and refrigerate at least 45 minutes before slicing.