Line a 9x13 inch pan with foil; butter and set aside.
Combine all ingredients except rum extract in a large (4 qt.) saucepan.
Cook over medium heat, stirring occasionally, 15-20 minutes or until butter is melted and mixture comes to a boil.
Attach a candy thermometer to the side of the pan. Continue cooking, without stirring, 25-30 minutes or until candy thermometer reaches 244 degrees (firm ball stage).
Remove from heat; stir in rum extract.
Pour into prepared pan and cool completely.
Cut into small pieces; wrap in wax paper.
Store in the refrigerator.
*Recipe adapted from Land O Lakes' Soft Caramel Recipe
*I found it VERY helpful to test my candy thermometer for accuracy - it made ALL the difference! To test: boil water in a large pot. Thermometer should register at 212 degrees when water starts to boil. When I did this (after 3 failed attempts) I discovered that my thermometer registered at only 200 degrees...meaning I needed to adjust accordingly!