Line the bottom and sides of the baking pan with aluminum foil and grease the foil. If using the walnuts, spread them in the prepared pan. Set aside.

Combine the corn syrup, honey, sugar, and salt in a heavy 3-quart saucepan. Cook over medium heat, stirring with a silicone spatula or wooden spoon, until the mixture simmers around the edges. Wash the sugar and syrup from the sides of the pan with a wet pastry brush. Cover and cook for 3 minutes. (Meanwhile, rinse the spatula or spoon for use again later.) Uncover the pan and wash down the sides once more. Attach the candy thermometer to the saucepan, without letting it touch the bottom of the pan, and cook, uncovered, without stirring until the mixture reaches 305°F.

Meanwhile, heat the cream in a small saucepan until tiny bubbles form around the edges of the pan. Turn off the heat and cover the pan to keep the cream hot.

When the sugar mixture is at 305°F, turn off the heat and stir in the butter chunks. Gradually stir in the hot cream; it will bubble up and steam dramatically. Turn the burner back on and adjust it so that the mixture boils energetically but not violently. Stir until smooth. Continue to cook, stirring occasionally, to about 245°F. Then cook, stirring constantly, to 248°F for soft chewy caramels or 250°F for firmer chewy caramels.

Remove the pan from the heat and stir in the vanilla. Pour the caramel into the lined pan. Let set for 4 to 5 hours, or overnight, until firm.

Lift the pan liner from the pan and invert the sheet of caramel onto a sheet of parchment paper. Peel off the liner and turn the caramel right side up. Cut the caramels with an oiled knife into 1-inch squares, skinny bars , or any desired shape. Wrap each caramel individually in wax paper or cellophane.