In a medium saucepan, melt butter over medium-low heat. Add brown sugar and light Karo syrup. Cook for 5 minutes or until silky smooth and glossy.
Remove from heat and chill for 15 minutes or until it cools to room temperature.
Add vanilla and eggs and whisk well to combine.
Stir in pecan halves.
Pour into prepared pie shell. Put on baking sheet.
Bake for 45 - 55 minutes or until filling is cooked and pie crust is lightly golden brown. Check halfway through cooking time and add pie shield or foil to cover pie crust to prevent too much browning. If you are using a deep dish pie pan, you may need to cook it 5 minutes longer.
Let it come to room temperature to set-up. This can be refrigerated to chill and firm up. Serve with fresh whipped cream.
Whipped Cream:
In a mixing bowl, whip heavy cream until soft peaks form. Add powdered sugar and whip until stiff peaks form.