Lightly butter an 8" square pan.

Heat cream to luke-warm in a large heavy sauce pan. Once warm, pour out half the cream into another container and set aside.

Add sugar, corn syrup and salt to the cream in the saucepan. Cook over medium heat, stirring constantly, until mixture boils.

Slowly add the cream that you set aside into the sauce pan, so the mixture doesn't stop boiling.

Cook for 5 minutes, stirring constantly. Add butter and lower temperature but keep it boiling gently and continue to stir.

When temperature teaches 248F, remove from heat. Mix in vanilla (and optionally nuts) and let stand for 10 minutes.

Pour into pan and let cool to room temperature; remove from pan onto a cutting board and cut into pieces with a sharp knife. Wrap each piece in wax paper.