Mix brown sugar, butter, corn syrup and salt. Cook and stir until it bubbles around the edges. Cook 5 more minutes.
Add baking soda and stir until foamy.
Pour half the mixture over each pan. Divide the peanuts and stir into each pan, stirring until corn is covered. Bake for 1 hour, stirring every 15 minutes.
VARIATION: To make jello popcorn, omit brown sugar and add 2 small boxes of jello.