"I'm absolutely fascinated by mushrooms," said Tom Peterson. It shows. In meticulously managed indoor and outdoor environments, the owner of Birch Creek Forest Products in Burnsville cultivates 19 mushroom species, year-round. Peterson's hard work is paying off, with a clientele of chefs and shoppers that's spreading faster than morels in springtime. "Just ask anyone at the farmers market where the mushroom guy is," he said. "They know who I am."