Preheat oven to 350° F. Spray an 11'' x 17'' sheet pan with cooking spray and set aside.

Microwave chocolate and water in large microwaveable bowl for 1-1/2 to 2 minutes, or until chocolate is almost melted, stirring after 1 minute. Stir until chocolate is completely melted.

In a small bowl, beat egg whites with a mixer on high speed until stiff peaks form. Set aside.

In a separate bowl, mix flour, baking soda, and salt. Set aside.

In a large bowl, beat butter and sugar with mixer until light and fluffy. Add egg yolks, 1 at a time, beating well after each addition. Blend in melted chocolate and vanilla. Add flour mixture alternately with buttermilk, beating until well blended after each addition. Add egg whites and stir gently until well blended.

Spread evenly into prepared pan and bake for 28 to 30 minutes, or until toothpick inserted in center comes out clean. Place on wire rack and immediately brush hot cake with chocolate glaze.

Prepare the glaze while the cake is baking. In a small saucepan over medium heat, melt butter and cocoa. Add powdered sugar and milk, stirring well. Heat to boiling and then remove from heat. Add vanilla and stir well.

With a large pastry brush, gently brush the glaze over the hot cake. Let cake cool completely before adding the coconut-pecan frosting.

In a large saucepan, beat egg yolks, evaporated milk, and vanilla with wire whisk until well blended. Add sugar and butter, and cook over medium heat for 12 minutes, or until thickened and golden brown, stirring constantly.

Remove pan from heat. Add coconut and pecans, mixing well. Let cool to room temperature and of desired spreading consistency. Then spread frosting evenly over cooled cake.