The core of the initiative is a "mini safe" embossed with the words "hands off" and designed to hold a single cake to encourage lunchbox use. Responsibility for building awareness of the promotion, which will be carried on 4.5 million six-packs of mini rolls, rests with a series of television commercials that parody public information films from the 1950s.
The agency that created the campaign is as distinctive as the ads it has produced. The Advertising Brasserie is not the only organisation in its industry to have eschewed the traditional policy of taking its name from those of its founders. Nor is it the only one claiming to be offering a variety of communications and marketing services. But where it does appear to be different is in challenging the way in which advertising works.
Operating under the slogan of a "task-driven approach to breakthrough advertising ideas", the small organisation, based just off London's Oxford Street, seeks to distinguish itself from its rivals by getting away from what it sees as the usual service-based relationship. This typically entails clients signing up for a two-year arrangement with a particular agency in return for a monthly fee.
Mischa Alexander, one of the four founding partners, says: "That way of working is fine for a lot of clients, but it is clearly not right for everyone." He and his colleagues - who have all worked together for several years - would rather think in terms of dealing with a client's needs of the moment, typically coming up with an idea. Operating in this way, he maintains, "forces you to think in terms of the value of what you're doing".
The other benefit of setting up as an "ideas factory" rather than a provider of general advertising services is that it enables the partners to stay in contact with the client. "We are a small team of senior people," says Mr Alexander. "We have deliberately chosen to have this type of business, rather than be managers in large agencies."
The brasserie idea is not entirely new. Mr Alexander, whose speciality is account management and business development, set up something similar when he was working at Howell Henry Chaldecott Lury with Chris McDonald, a planning and strategy specialist, and the creative team of Dave Shelton and Liz Waldron . Then - when the market was buoyant - the brasserie was seen as complementary to the main agency. The foursome got their chance to see if the idea worked as a stand-alone when HHCL was bought by Chime Communications two years ago and they left by amicable agreement.
The past two years have, they say, been successful according to their own three yardsticks: they have a profitable business; they have produced a series of innovative campaigns for blue-chip clients - including the Disney cable channel, the pubs and hotels group Bass and the foods firm RHM; and they have had fun doing it, says Mr Alexander.
The workforce has grown from the original quartet to only 12 staff. But all concerned stress that an important part of the way they operate is bringing in expertise when it is needed.
"A lot of large accounts are recognising the distinction between ideas and service, and that they may not get those in the same place," says Mr Alex-ander. Then it is possible for the brasserie, say, to come up with an idea that is then looked after by a different agency, rather like strategic management consultants may identify a market but then leave it to another firm to implement the strategy.
In such a way, the brasserie can produce a sustainable business without growing to such an extent that the basic attraction - of selling creative skills - is lost.
As Mr McDonald says: "If we followed the traditional model we would probably have 30 people already. But we're convinced we don't need to as we deliver things differently."
One of the clearest differences - apart from the fact that the agency's office abandons the traditional flashy reception area - is the policy of filming its own ads. This is usually contracted out to specialist production firms - a policy that can cause delays and add to the distance between film maker and client. But the brasserie claims it can reduce delays and increase flexibility at the same time as making the client more involved.
So far, the approach seems to be working. Ads for Paxo, designed to show how the stuffing could be used on its own, are claimed to have have halted a long-term decline in market share. Another humourous ad, aimed at informing viewers of the merits of McCain's pizzas, elicited an unprecedented customer response.
Time will tell if the trick will be repeated with Cadbury's 30-year- old Mini Rolls. But a strong marker has been put down.