Line three sheet trays with foil and spray with cooking spray, set aside.
Place the butter, granulated sugar, brown sugar, heavy cream, corn syrup, and salt into a large pot or dutch oven.
Place over medium-low heat and let the butter melt and sugars dissolve, stirring occasionally. Turn the heat up to medium stirring occasionally (make sure to scrape the bottom of the pan so nothing sticks) and bring to a low boil. Cook and stir occasionally until a candy thermometer reaches 236°F (soft ball stage) about 6-7 minutes.
Remove from the heat and add in the pecan halves, chopped pecans, and vanilla extract.
Stir in then do not stir again, allow the temperature to come down to 170°F, about 15 minutes.
Stir it around with a wooden spoon for about a minute to slightly let it cool, the mixture will still appear slightly glossy but will start thickening.
Immediately dollop heaping tablespoons of the mixture onto the prepared sheet trays not touching. Let them rest and harden for about 8 hours or overnight. Serve immediately.
Notes
These need to set up for 8 hours.
You can speed up the setting process by putting them in the refrigerator.
These can be frozen, see my tips above on how to do this.
Make sure you use a large pan so the sugar mixture does not bubble over.