Remove all unpopped kernals from the popped corn. Place popcorn on a greased 17x12x2-inch baking pan. Keep popcorn warm in a 300˚F oven while making caramel mixture.

​Butter the sides of a heavy 1½ quart saucepan. In saucepan combine brown sugar, butter and corn syrup. Cook and stir over medium heat to boiling. Clip candy thermometer to side of pan. Cook and stir over medium heat to 255˚F, about 4 minutes.

Remove the saucepan from the heat. Stir in baking soda and vanilla; pour over popcorn. Stir gently to coat all kernels, add the peanuts and mix gently. Bake in a 300˚F oven for 15 minutes; stir. Bake 5 more minutes. Transfer popcorn mixture to a large piece of foil; cool completely. Break into clusters.

Serve or store tightly covered.