Preheat oven to 350°F. Grease and line three 9-inch cake pans.

Melt white chocolate in microwave in 20-second bursts; cool 5 minutes.

Whisk flour, baking soda, and salt.

Beat butter until creamy; add sugar gradually. Add egg yolks.

Mix in melted white chocolate and vanilla.

Alternate adding flour mixture and buttermilk, beginning and ending with flour.

Beat egg whites to medium-stiff peaks; fold into batter.

Divide batter among pans and bake 20–22 minutes; cool completely.

For frosting: toast pecans. Cook evaporated milk, sugars, butter, and egg yolks 10 minutes until thick. Add vanilla, coconut, and pecans. Cool 1 hour.

Spread frosting between cake layers and over top and sides. Add optional cheesecake layer in center if desired.