Line a 13x9-inch pan with foil and generously butter with 1 tablespoon butter.
Mix all ingredients EXCEPT vanilla in a large 6 to 8-quart pan.
Boil over medium heat, stirring constantly. Reduce heat to medium-low and continue cooking, stirring occasionally until temperature reaches 244ºF. Remove from heat and stir in vanilla.
Pour into prepared pan. (Do not scrape sides of bowl).
Cool to room temperature. Invert cooled caramel onto cutting board and remove foil.
Cut into 1-inch squares. Wrap in wax paper or plastic wrap. Store in airtight container.
Recipe suggestion: Try adding 2 cups of finely crushed nuts.