Possibly the best caramel corn you have ever had.

Bring to boil (30 - 45 seconds) the butter, brown sugar and corn syrup.
Take off stove and immediately add vanilla and baking soda. Stir quickly until it foams.
Pop the microwave popcorn. Remove the grannies.
Spray the inside of the grocery bag with Pam, and place the popcorn on the bottom.
Pour boiled mixture into the bag , shake to mix, fold over the top and microwave on high for 1 1/2 minutes.
Shake bag again and microwave another 1 1/2 minutes.
Shake again and microwave for 30 seconds.
Shake again and microwave for 30 seconds.
Shake again and spread out on cookie sheets to cool.
Break apart and store in airtight container.