Pop popcorn according to package directions.
Place popped corn into a 4 to 6 quart (large) microwave safe bowl; set aside.
In a separate microwave safe measuring cup or bowl, combine brown sugar, butter, syrup and salt.
Microwave on high for 1 ½ minutes; stir.
Microwave on high again for 1 minute more; stir.
Add baking soda and vanilla; stir well (will bubble up).
Immediately pour this mixture over popcorn, stirring to coat evenly.
Microwave coated popcorn mixture for 1 minute on high; stir.
Microwave 1 more minute on high and stir well.
Turn out onto waxed paper and allow to cool completely.
Break into pieces.
*Brenda’s tip: Make in original small batches. Use fresh popped corn, still warm.