Coat sides of a Dutch oven with 1 tablespoon butter. Add brown sugar and next 4 ingredients. Bring to a boil over medium heat, stirring constantly until sugar dissolves (about 5 minutes). Cover and cook, without stirring, 2 to 3 minutes to wash down sugar crystals from sides of pan. Uncover and cook, stirring occasionally, 10 to 12 minutes or until mixture reaches soft ball stage (234°). Remove from heat; stir in 1/2 cup butter and vanilla.
Beat with a wooden spoon 5 minutes or until mixture is creamy and begins to thicken. Stir in pecans. Working quickly, drop mixture by heaping tablespoonfuls onto lightly greased wax paper; let stand until firm.