Cadbury has produced a white chocolate version of its Easter Creme Egg for the first time - but consumers will not know if they have bought one until they unwrap it.
Between 350 and 400 of the white eggs are on sale in the same packaging as the standard milk chocolate version until Easter Sunday on April 1, with Cadbury offering cash prizes to those who find one.
They are being stocked by selected independent and convenience retailers such as local newsagents and corner shops and in Sainsbury's Local, Tesco Express and Co-op branches until Easter Sunday on April 1, with each one worth at least £100, Cadbury said.
The promotion is bound to cause some consternation among fans of the product, who claimed that Cadbury's US owners ruined Easter two years ago with a new "cheap chocolate imitation" Creme Egg.
It followed brand owner Mondelez changing the recipe for the sweet fondant-filled snack so that the shell is made from a "standard, traditional Cadbury milk chocolate" instead of the popular Cadbury Dairy Milk.
Early response to the white egg on social media was mixed, with Tara Evans writing: "Cadbury's has gone all Charlie and the Chocolate factory on us".
Sami Harper posted: "Desperately need to find and eat a white Cadburys creme egg, couldn't care less about winning any money from it," but another person described it as "an abomination".
Consumers were bemused to see Easter Eggs on shop shelves almost immediately after Christmas, but Creme Eggs went on sale on New Year's Day, which is standard for the product.
US giant Kraft Foods bought Cadbury in 2010 and its global snacks business under the name of Mondelez International.
The now familiar Cadbury Creme Egg first hit the shelves in 1971.
A single Creme Egg costs 58p, while a five-pack costs £2.85 and a twelve-pack costs £6.68.