In a large pot, add butter and heavy cream.
Add the corn syrup to the middle of the pot and allow it to settle in a bit.
To the center of the pot, add the sugars, being careful to avoid getting sugar on the sides of the pan. If this happens, use a pastry brush moistened with melted butter or water and gently brush the sides of the pan to get the sugar off the sides.
Allow this to sit in the pan for a few minutes to allow the cream to start working its way into the sugars.
During this time, prepare a 9 X 13 baking dish by spraying it with baking spray. Cover the pan with non-stick foil or parchment paper and spray that with baking spray as well.
I use 2 sheets of parchment paper, one cut as wide as the long side, and one cut as wide as the short side. I place those in the pan leaving an overhang on all four sides.
Once the pan is prepared, add vanilla, if using, to a small bowl set near the stove.
Gently start pushing the sugar mound down into the moistened sugar on the bottom, again being careful not to get sugar on the sides of the pan, use the above method if it does happen.
Turn heat to medium and cook, stirring occasionally until mixture begins to boil. This will take 15 to 25 minutes depending on your idea of medium heat and the weather. I find it takes a little longer in humid weather and even longer on rainy days.
Once it begins to boil, clip a candy thermometer to the side of the pot.
Begins stirring constantly until candy thermometer reads firm ball stage or 244°F. This can take 25 to 45 minutes, again this is dependent on exact heat and weather.
Once the candy is ready, turn off the heat and add vanilla if using. Up to ½ cup of chopped nuts can also be added if desired.
Immediately pour into prepared pan, being very careful, this mixture is very hot.
Allow caramel to cool completely in pan.
Once cool, remove from pan and cut into the desired size. I usually get 90 to 100 two to three bite caramels.
Wrap each caramel in wax paper or candy wrapper.