Line an 8-inch baking dish with parchment paper and spray with cooking spray. Set aside.

To a medium saucepan over medium heat, add the sugar, corn syrup, butter, and ½ cup heavy cream.

Bring to a boil, stirring constantly, about 5 minutes. Do not leave unattended, and adjust the heat as needed to prevent the mixture from boiling over.

While stirring, add the remaining heavy cream. Continue stirring and, using a candy thermometer, bring the mixture to 240°F, about 30 minutes.

Remove from the heat and stir in the vanilla.

Immediately use a toothpick to pop any air bubbles that rise to the top. Let sit at room temperature overnight to set. Or, chill it in the refrigerator for at least an hour.

Once set, remove the caramel from the pan and cut into pieces. Wrap individually in wax paper if desired.