Preparation Line 9-inch square baking pan with 2-inch high sides with heavy-duty aluminum foil, extending foil over sides of pan. Butter foil. Melt 1 cup of butter in heavy large saucepan over low heat. Add both sugars, corn syrup and sweetened condensed milk and stir until sugar dissolves. Scape seeds from vanilla into mixture; add bean. Attach clip-on candy thermometer to side of saucepan. Increase heat to medium and bring mixture to a boil. Cook mixture 8 minutes, stirring frequently. Using tongs, remove vanilla bean and discard. Continue cooking until candy thermometer registers 242°F, stirring frequently, about 5 minutes longer. Immediately remove from heat; stir in hazelnuts. Quickly pour caramel into prepared pan (do not scrape saucepan). Cool until firm, about 1 hour. Using buttered heavy large knife, score 8 lines lengthwise to depth of 1/4 inch in caramel, then score 8 lines crosswise. Using aluminum foil as aid, lift caramel out of pan. Using same buttered heavy large knife, cut caramel on scored lines into pieces. Wrap each piece of caramel in cellophane. (Can be prepared 2 weeks ahead. Store caramels in airtight containers.)
Preparation Line 9-inch square baking pan with 2-inch high sides with heavy-duty aluminum foil, extending foil over sides of pan. Butter foil. Melt 1 cup of butter in heavy large saucepan over low heat. Add both sugars, corn syrup and sweetened condensed milk and stir until sugar dissolves. Scape seeds from vanilla into mixture; add bean. Attach clip-on candy thermometer to side of saucepan. Increase heat to medium and bring mixture to a boil. Cook mixture 8 minutes, stirring frequently. Using tongs, remove vanilla bean and discard. Continue cooking until candy thermometer registers 242°F, stirring frequently, about 5 minutes longer. Immediately remove from heat; stir in hazelnuts. Quickly pour caramel into prepared pan (do not scrape saucepan). Cool until firm, about 1 hour. Using buttered heavy large knife, score 8 lines lengthwise to depth of 1/4 inch in caramel, then score 8 lines crosswise. Using aluminum foil as aid, lift caramel out of pan. Using same buttered heavy large knife, cut caramel on scored lines into pieces. Wrap each piece of caramel in cellophane. (Can be prepared 2 weeks ahead. Store caramels in airtight containers.)