The recipe I've always used. (below)
Instead of 1 cup brown sugar, I used regular sugar, and added 1 pkg Raspberry unsweetened Kool-Aid. It is really good.
1/2 cup popcorn (I use 2 bags microwave popcorn)
Put popped corn in a large clean grocery bag.
1 stick butter
1 cup brown sugar
1/4 cup karo syrup
1 tsp. vanilla
Cook in microwave on high 4 minutes.(I use my 6 cup glass measure with a spout, so it's easier to pour)
Add 1/2 tsp bkg. soda. Stir til foamy. Pour syrup over popped corn in paper bag. Shake, fold top of bag down, and microwave 1 min., take out shake again and microwave 1 min. more. Pour into bowl. I've never had a problem with this recipe.