Lightly spray a 9"x13" pan with cooking spray and set aside. If you want to be able to lift the full slab of caramel out of the pan to cut it, line pan with parchment paper, leaving an overhang on the long sides.

In a large heavy sauce pan over low to medium heat, melt the butter. Add sweetened condensed milk, sugar, corn syrup, and salt. Place a candy thermometer on side of pan, taking care to not let it touch bottom of pan. Stirring almost constantly, cook on medium heat to 234° F to produce a soft and chewy caramel. Cook up to 244° F for a firmer caramel. 

Remove from heat and stir in anise extract and black food coloring. Pour into prepared pan and let cool for 30 minutes on the counter.

Place in refrigerator to cool completely. Cut into pieces (mine are about 3/4" x 2"). Wrap in wax paper. Enjoy!