This dark beer gets its deeper richer flavour from the use of roasted malt or roasted barley. Stouts and porters are essentially interchangeable these days, although when producers use ‘stout’ it’s generally a stronger (higher alcohol) porter. Other styles of stout include milk stout, which contains lactose, a sugar derived from milk; Irish stout, dryer than English or American stouts, and made famous by Guinness; and chocolate stout, made from the darkest of roasted barley or malt, with a chocolate flavour.