In a bowl, mix egg yolks, 1/2 cup sugar and cornstarch on medium-high speed until mixture is thick and pale.
Bring coconut milk, the other 1/2 cup sugar, chopped Purdys White Chocolate and vanilla extract to a simmer in a medium pan over medium-high heat.
Turn mixer on medium-low and slowly pour milk mixture into egg yolk mixture. Transfer to saucepan.
Cook mixture over medium-heat, whisking constantly until boiling.
Remove from heat and strain through a fine sieve into a bowl. Let cool completely.
In separate bowl, beat butter until creamy then add a tablespoon of cooled cream mixture. Continue adding cream mixture and beating on medium-low.
Add coconut flakes and mix well.
Slice cake horizontally into layers. Spread cream on one layer, then add another layer on top, repeating until finished. Spread remainder of the cream mixture on the outside of the cake and decorate with Snowballs as desired or as pictured.