In a saucepan over medium heat, combine milk and sugars. Bring to a boil, stirring constantly.

Continue cooking without stirring until 237°F.

Remove from heat, add butter and vanilla but do not stir. Allow mixture to cool to 110 degrees F or until pan feels lukewarm, about 40 minutes.

Butter an 8" square pan.

Using a wooden spoon, beat mixture until it thickens and looses glossy look. Stir in the pecans and pour into prepared pan. Do not scrape sides.

Cut with a knife into squares. Serve once it sets completely.