Sift through popcorn to remove all kernels. Place popcorn in a 17" x 12" or larger greased baking pan. Place pan in a 300º oven. In a 4-quart heavy saucepan, combine brown sugar, butter and corn syrup. Mix thoroughly. Cook over medium heat to boiling. Cook to 255º. Remove from heat and stir in baking soda and vanilla. Gently stir in popcorn. Spread popcorn back into baking pan and place in oven for 15 minutes, stirring every 3 minutes. Spread onto silicone mat or parchment sheet. Break into pieces when cool.
For deluxe popcorn, stir 1/2 pound commercial caramel into the hot syrup when adding the soda and vanilla. 1 1/4 cups nuts may also be added at this time. After caramel corn is cooled, drizzle 1/2 pound chocolate over the caramel corn. Let set up, then break into pieces.
Recipe and image taken with permission from Autumn Carpenter's Book, All About Candy Making. All rights reserved.