Karen Akunowicz started cooking to impress a girl. Now, her kitchen nickname is Chainsaw and she’s one of the best-known chefs in the United States. For almost five years, she has been the Executive Chef at celebrated Boston restaurant Myers + Chang, she was just nominated for a James Beard award for Best Chef Northeast for the second year in a row, and she carves out space for herself on the current season of Bravo’s Top Chef.