I found this recipe* at The Amateur Gourment blog and have made it a handful of times with great success. Be careful not to boil the caramel too long or it burns and tastes bad. Also, don't bake it too hot or too long because this will give a burnt taste too.
*I think I might have already posted this recipe somewhere (I'm having feelings of deja vu) but don't remember where (typical momnesia!).
Never fail caramel corn.
1 cup butter
1/2 cup corn syrup
1/2 tsp baking soda
2 cups brown sugar
1 tsp salt
1 tsp vanilla
6 quarts of Popped corn(use the kind labeled Mushroom popcorn)
Heat your oven to 250F. Melt the butter, stir in the corn syrup, sugar and salt. Bring the misture to a boil stirring constantly. Boil without stirring for 5 minutes. Remove from the heat, stir in the soda and vanilla (Careful! it foams!). Pour over the popped corn and mix well. Spread the coated corn into large cake pans and bake for 40 minutes, stirring every 10 minutes. Let it cool and eat! You can add peanuts or any other nuts if you like.