To prepare the toasted coconut: Bake sweetened flaked coconut at 350°F on a sheet tray until golden brown (7-10 mins). Do not leave unattended, coconut can burn quickly.
To prepare the custard: In a medium saucepan, combine sugar and cornstarch. Gradually add milk, stirring until smooth. Cook over medium heat until thick. Temper egg yolks by adding some hot mixture to them while mixing. Blend well and slowly add yolks to hot mixture off the heat. Cook until thickened (10-12 mins) and remove from heat. Add vanilla, butter, salt, and toasted coconut. Stir well and let cool completely, then chill.
To prepare the crust: Combine wafer crumbs, toasted coconut, melted butter, and sugar until mixed. Press into a 9×13 pan and chill.
To prepare the cream cheese layer: Beat cream cheese, sugar, and milk until smooth. Set aside.
To prepare the whipped cream topping: Whip cream, powdered sugar, sour cream, and vanilla until stiff peaks form. Keep chilled.
ASSEMBLY: Spread cream cheese mixture on crust, then spoon chilled coconut custard on top. Chill for 30 minutes. Whip cream mixture and spread on dessert. Chill for 1-2 hours to set. Garnish with toasted coconut.