Spread hazelnuts in a single layer on a 15" x 10" jelly-roll pan. Bake at 350° for 5 to 10 minutes or until skins begin to split. Transfer warm nuts to a colander; using a towel, rub briskly to remove skins. Coarsely chop nuts.
Cook sugar and next 3 ingredients in a large heavy saucepan over medium heat, stirring constantly, until mixture starts to boil. Boil without stirring until a candy thermometer registers 290°. Carefully stir in nuts using a clean spoon. Remove from heat, and stir in banana chips and remaining ingredients. (Baking soda will cause candy to foam.) When foaming subsides, quickly pour candy onto a buttered baking sheet. Pour as thinly as possible without spreading. After 2 to 3 minutes, use 2 buttered forks to stretch and pull brittle as fast as possible before brittle starts to break. Cool completely, and break into irregular size pieces. Store in an airtight container.