Heat oven to 350 degrees. Lin 15x10x1 inch pan with waxed paper, grease generously with shortening. Heat chocolate and water in a saucepan over medium heat, stirring constantly until chocolate is melted, cool. Mix flour, baking soda, and salt. Set aside.
Beat sugar and butter in a bowl with mixer on low speed 30 seconds, scrapping bowl. Beat on high for 3-5 minutes until light and fluffy. Beat in eggs, one at a time, until smooth. Beat in chocolate and vanilla. Beat in flour mixture alternately with buttermilk, beating after each addition until smooth. Pour into pan.
Bake 13-16 minutes or until toothpick comes out clean. Immediately loosen cake from edges of pain, cool 10 minutes. Place towel on wire cooling rack, sprinkle generously with powdered sugar. Turn pan upside down onto a towel to remove the cake. Carefully remove waxed paper or foil. Cool completely for at least 30 minutes.
Make Coconut Pecan Filling and Chocolate Ganache. Cut cake crosswise into thirds. Place 1 cake piece, sugared side down on a serving platter. top with half of the filling. Add second piece, sugar side down, top with remaining filling. Add third piece, sugared side down, spread ganache.