01 - Preheat oven to 350°F. Grease and line three 8-inch round cake pans with parchment paper.
02 - Whisk together flour, baking powder, and salt in a medium bowl.
03 - Cream butter and sugar in a large bowl until light and fluffy, about 3 minutes. Add eggs one at a time, beating well after each addition.
04 - Beat in melted, cooled white chocolate and vanilla extract until just combined.
05 - Add flour mixture to wet ingredients in three parts, alternating with milk, beginning and ending with flour. Mix until just combined; do not overmix.
06 - Divide batter evenly among prepared pans. Bake for 22-26 minutes or until a toothpick comes out clean. Let cakes cool in pans for 10 minutes, then turn out onto racks to cool completely.
07 - Combine sugar, evaporated milk, egg yolks, and butter in a medium saucepan over medium heat. Cook, stirring constantly, until thickened and golden, about 10-12 minutes.
08 - Remove from heat. Stir in coconut, pecans, vanilla, and salt. Let cool to room temperature.
09 - Place one cake layer on a serving plate. Spread with one-third of the coconut-pecan filling. Repeat with remaining layers and filling. Garnish with chopped white chocolate, coconut, or pecans if desired.
10 - Chill cake for 1 hour before slicing for cleaner cuts.