1. Line a 9 x 13 pan with buttered foil.
2. In a heavy saucepan, combine 1 cup butter, sugars, corn syrup and 1 cup of heavy cream.
3. Stir over medium heat until the sugars are dissolved.
4. Bring mixture to a boil, then slowly stir in remaining cup of heavy cream.
5. Using a Candy Thermometer, bring mixture to 240 degrees, without stirring.
6. Remove from heat, stir in pecans and vanilla.
7. Pour mixture into prepared pan.
8. Allow to cool, remove from pan and cut into 1 squares.
9. Wrap in parchment paper, plastic wrap or just store in a Ziploc bag.