Phil "Doc" McDonald reckons his cold-brew coffee is almost like a drug - and he has to be careful not to drink his supply.
Mr McDonald, who owns Doc's Coffee House in Dunedin's Albany St, believes he is the only producer of cold-brew coffee in New Zealand. Production began a month ago, with retail sales from the coffee house starting two weeks ago.
Mr McDonald, a keen follower of international boutique coffee businesses, stumbled upon cold-brew "almost by mistake".
He discovered it was being made by one of the US companies he followed, Stumptown, in Portland, and decided to give it a go.
There were several companies in New Zealand that made cold-drip coffee, which involved an eight to 10 hour process, but he was not aware of anyone doing cold-brew.
Single-origin organic coffee was combined with pure, filtered water, distilled for 21 hours and strained three times to remove any impurities. The resulting brew was sold in bottles.
Mr McDonald spent six months on research and development, changing ratios and quantities, but never tired of sampling the cold brew.
"I love it more and more," he enthused.
Born and raised in Dunedin, Mr McDonald's interest in coffee began in 1999 while he was studying at Otago Polytechnic. Several of his friends worked at Ruby In The Dust in the Octagon, where he started drinking coffee.
The coffee scene was "nothing back then" and the focus was on volume, not quality, leading him to wonder why people did not do a better job of it.
Mr McDonald later moved to Auckland, where he got a job at an Italian restaurant. He talked his way into a coffee-making job, and was soon brewing 300 cups a day.
He later worked in a cocktail bar in Ponsonby and that was where he learned quality rather than quantity was the key in the hospitality industry.
Mr McDonald returned to Dunedin in 2007 and opened Doc's Coffee House in June last year. It was an opportunity to work in an industry he was passionate about, selling a product he was passionate about, he said.
He was pitching the cold-brew coffee at coffee-lovers who wanted to try something new and also to people too busy to "whip out" and buy coffee.
It had a variety of uses and could be enjoyed straight, on the rocks, with water or milk, hot or cold or even mixed with vodka.
Ideally, he would like to see it available in the future in other specialty coffee houses and boutique bars. With a whisky-type texture, it filled a void among non-alcoholic drinks.
"It's different. There's nothing else like it readily available," he said.
Already, other cafe owners and baristas from "all over town" had been to Doc's Coffee House to try it. At this stage, it was the only outlet for cold-brew.
Quantities being produced changed each week but had increased every week. Sales were better than initially expected.
In the future, Mr McDonald hoped he might be able to "step away from being behind the coffee machine" to concentrate on making cold-brew.