Combine 2 cups coconut, graham cracker crumbs, and melted butter. Press onto bottom and side of 9-inch pie plate. Bake for 10 minutes. Cool.
In large saucepan, combine milk and 1 cup coconut. Bring just to simmering, stirring occasionally. In large bowl, combine egg yolks, granulated sugar, and flour. Beat with electric mixer on medium-high speed until combined. Slowly stir about 1 cup of the hot milk mixture into yolk mixture. Return yolk mixture to saucepan. Bring to boiling, stirring often. Cook and stir for 2 minutes more. Remove from heat. Stir in 2 tablespoons creme de cacao and 1 tablespoon butter. Cover surface of filling with plastic wrap; cool.
Meanwhile, in small saucepan, cook and stir white chocolate and 1 tablespoon cream over low heat until melted. Spread onto bottom and side of piecrust. Chill until firm. Pour filling into crust. Cover and chill for 2 to 4 hours.
In chilled medium bowl, beat 2 cups cream, powdered sugar, and, if desired, 1 tablespoon creme de cacao until stiff peaks form. Spread topping over filling. (If pie isn't served all at once, top only the pieces to be served with topping. Chill remaining topping and pie separately.) If desired, garnish with coconut curls. Makes 8 servings.