Mix together the popped corn and the peanuts in a very large bowl or a roast pan.
Keep warm in a 250 degree oven.
Melt butter in a heavy 2 quart saucepan.
Stir in the brown sugar, corn syrup and salt.
Bring to a rolling boil, stirring constantly.
Boil without stirring for 5 minutes.
Remove from the heat.
Stir in baking soda and vanilla.
Quickly pour over warm popcorn and peanut mixture while tossing until popcorn and nuts are well coated.
Spread out in a shallow baking pan or cookie sheet.
Bake at 250 degree for 45 minutes.
Stir about every 15 min.
Make sure every piece of popcorn has been moved around on the bottom.
Remove from the oven.
Turn out on aluminum foil to let it cool.
Store in a tightly covered container.