It is the opposite of "White
Trash". Someone who is an upstanding example of American and all that is amazing about being white. Underlying connotation would be extremely
sarcastic and moderately pejorative, as is the common usage
case.
1) Mike just dominated in flip cup, he is such a White Treasure.
2) Only a White Treasure could
shotgun a
beer, puke off the balcony, and then rally.
3) Dude you have to get the 7 pound chili cheese
dog, its a White Treasure.