In a small saucepan over medium heat, combine half of the brown sugar and the pecans.

Cook until pecans are slightly fragrant, then add the water and remaining brown sugar. Stir well to dissolve sugar.

Allow mixture to come to a simmer, then reduce and simmer over medium-low heat until reduced by half.

Remove from heat, and if desired, stir in 1/2 teaspoon vanilla extract.

If desired, strain the pecans out of the mixture before storing in a sealed container in a cool spot.