Combine butter, corn syrup, sugar and salt in an 8 cup bowl. Microwave on high, 1-2 minutes or until it bubbles. Boil for 3 minutes, stirring after each minute. Add baking soda and vanilla, stir well, pour over popcorn.
Shake well, fold-down bag and microwave on high for 1 minute. Shake well. Microwave on high for 1 minute. Shake well. Microwave on high for 30 seconds. Shake well. Microwave on high for 30 seconds.
Place on wax paper and let cool. Store in an airtight container!
Find it online: https://livelaughrowe.com/homemade-caramel-popcorn/