Toast Pecans: Spread pecans in a single layer on a standard cookie sheet. Toast in a 350°F oven for 6-8 minutes, then cool.
Make Icing:In a heavy bottomed saucepan over medium high, melt together butter, milk, granulated and brown sugar, corn syrup and salt.
Cook until the sugar has dissolved then lower the heat to medium.
Whisk 1/4 cup of the warm liquid into the egg yolks to temper, then whisk the egg yolks into the saucepan.
Cook over medium heat stirring until thickened around 12-15 minutes. The consistency should coat the back of a spoon like a thin pudding. [Tip: The icing will thicken more as it cools]
Remove from the heat and add the vanilla, toasted pecan pieces and coconut. Pour into a bowl and cool to room temperature to thicken before frosting cake.
Cake: Preheat the oven to 350°F. Cover the bottoms of 3 (9-inch) round pans with waxed paper; and spray sides with cooking spray.
Microwave the chocolate and water in a large microwaveable bowl on HIGH 1-1/2 to 2 minutes or until chocolate is almost melted, stirring after 1 min. Stir until chocolate is completely melted.
Beat egg whites in medium bowl with mixer on high speed until stiff peaks form; set aside.
In a separate medium bowl use a whisk to sift flour, cocoa powder, baking soda and salt.
Cream butter and sugar in large bowl with n electric mixer until light and fluffy. Add egg yolks 1 at a time, beating well after each. Blend in melted chocolate and vanilla.
To the creamed ingredients add flour mixture alternately with buttermilk, beating until well blended after each addition.
Add egg whites; fold in gently by hand until well blended. Pour into prepared pans.
Bake for 30 minutes or until a toothpick inserted in centers comes out clean. Immediately run small spatula around cakes in pans. Cool cakes in pans 15 minutes then remove from pans to wire racks. Cool completely.
Spread the coconut-pecan filling and icing between the cake layers, sides and onto top of cake. Store chilled.
Notes
The recipe makes enough icing to frost the cake completely, if desired.