You can now buy 100% cocoa chocolate on the High Street and sales are said to be on the rise. It's a rather acquired taste, so why is it becoming more popular and does real chocolate have to be high in cocoa to be good?
A "demanding and very powerful experience" is one description of eating chocolate with 100% cocoa content. "Pretty gruesome" is another.
The people who make it say it has flavour hints of anything from leather and tobacco to olive oil and oak. If that's what you want from a chocolate bar then you're in luck .
Chocolate with a very high cocoa content is increasingly being stocked in High Street shops, having largely been sold by specialist or artisan chocolatiers in the past.
Hotel Chocolat sells four different bars with 100% cocoa content in its branches, while Swiss company Lindt has 99% cocoa bars in UK shops and supermarkets.
The companies don't release sales figures for commercial reasons, but say there is a growing demand for the stuff.
"It's been a bit of a surprise success for us and at times we have found it difficult to keep up with demand," says Angus Thirlwell, co-founder of Hotel Chocolat. "The bars are now the strongest selling part of our premium range.
"People often try the bars out of curiosity and stay with them, others gradually migrate up the cocoa scale to the nirvana that is 100%."
Two of the nation's most popular milk chocolate bars, Cadbury's Dairy Milk and Mars Galaxy, have a minimum 26% cocoa and 25% respectively. Cadbury's dark chocolate Bournville has a minimum of 36% cocoa. It's what most people are used to eating, so what is with this growing obsession with 100% cocoa chocolate?
"People are waking up to the fact that chocolate is not a generic product," says Willie Harcourt-Cooze, owner of Willie's Cocoa, which also produces 100% cocoa chocolate.
"They are realising that different beans have different flavours, you can also use the same bean and change the way it tastes in the production process.
"You get wine connoisseurs, you get cheese connoisseurs, now there is a growing number of chocolate connoisseurs. A chocolate can be as complex and specialist as a fine wine."
It's helping boast the sales of most premium chocolate. Market analysts Mintel say "a notable pool of consumers are becoming more discerning when it comes to their choice of chocolate and are actively seeking out more top-end brands".
And with chocolate sales reaching £4bn in the UK in 2011, according to Mintel, even a niche market can create big profits.
But does a high cocoa content mean high quality chocolate? Does the rise in chocolate purism all come down to superior taste? Absolutely not, say experts.
"The problem is people confuse the two things," says Alasdair Garnsworthy, head chocolatier with the Chocolate Society.
"Chocolate with a high cocoa content can still be made using cheap beans. You can get chocolate with a lower cocoa content that is far better because it has been made with quality beans."
Using the best ingredients is much more important than cocoa content, say chocolate makers.
The origin of beans plays a big part, with certain types having a better flavour than others. Then there's how the beans are harvested and stored.
After that they are roasted and blended, then "conched". This is a process when beans - and other ingredients if used - are kneaded. The longer you do it, the better the flavour, says Garnsworthy.
"With cheaper chocolate the beans are conched for about 24 hours, with better quality chocolate it is done for around three days."
A lot of people are wrongly influenced by cocoa content because they don't know enough about chocolate to judge if it actually tastes good or not, say connoisseurs. It was the same with wine in the 1980s and coffee in the 1990s.
Better quality cacao tends to grow in places like South America, says Dom Ramsey, editor of Chocablog.
"If you're going for a high percentage chocolate bar, you should look for one that mentions the origin of the cocoa bean too. Single origin bars, from one country or even a single estate, have unique and distinctive flavour notes where bulk beans have very few."
The lower quality bulk cocoa beans are usually grown in West Africa, adds Ramsey. The trees produce a high yield but the beans don't have a lot of flavour.
Manufacturers add a lot of sugar to them in order to make them taste good. But the higher the cocoa content, the less sugar can be added to disguise bitterness.
"There is no place to hide when it comes to 100% cocoa chocolate," says Hotel Chocolat's Thirlwell.
"The recipe is cocoa beans, nothing else. No sugar, no vanilla. You can have different flavour profiles with different beans but they all have to be amazing quality to taste good."
Even among high-end brands, 100% cocoa chocolate divides opinion. Green & Blacks is acknowledged by some chocolate makers as "opening people's eyes to dark chocolate in the the UK".
Its biggest selling product in Britain is a 70% cocoa dark chocolate bar. Again, it won't release sales figures but says in the last year it has sold a bar every 10 seconds in the UK. You do the mathematics.
"We would never launch a 100% or 99% bar," says James Holloman, business leader for Green & Blacks in the UK. "This is because there is no balance in terms of the taste profile.
"Balance is about that cocoa hit and then the smooth feeling after. You get this by adding some sugar, vanilla and other elements. We think any dark chocolate with over 85% cocoa loses that perfect balance."
Others dismiss the increasing number of high-cocoa chocolates as "more of a gimmick" than anything else.
One thing is for sure, you can't stuff it down. Hotel Chocolat say it is best to eat two small pieces in succession, the first prepares your mouth and the second reveals the flavour.
Harcourt-Cooze, of Willie's Cocoa, says it is best used as an ingredient in food. He sells to many of the UK's top chefs who use it in dishes like venison with chocolate sauce.
But in general, the makers and lovers of fine chocolate are welcoming the move of high-cocoa chocolate from artisan chocolate shops to High Street ones.
"I think it's positive that the likes of Lindt has a 99% chocolate bar being sold in the local corner shop," says Ramsey.
"Not because this particular bar is great, but simply because it raises awareness and opens people's eyes to the fact that there's a world beyond Dairy Milk."