Coarsely chop 12 ounces chocolate; set aside. In a saucepan, heat cream over low heat until bubbles form around sides of pan. Remove from the heat; add chopped chocolate, stirring until melted and smooth.
Cool to slightly warmer than room temperature. Stir in butter and extract. Cover tightly and refrigerate for at least 6 hours or until firm.
Grate remaining 2 ounces chocolate; place in a shallow dish. Add nuts; set aside. Shape tablespoonfuls of chilled chocolate mixture into balls. Place on waxed paper-lined baking sheets. (If truffles are soft, refrigerate until easy to handle.) Roll truffles in chocolate-nut mixture. Store in an airtight container in the refrigerator.