Line a 13-in. x 9-in. x 2-in. baking pan with foil; butter the foil with 1 tablespoon butter. Sprinkle with pecans and chocolate chips; set aside. In a heavy saucepan over medium heat, melt remaining butter. Add brown sugar, corn syrup and water. Cook and stir until mixture comes to a boil. Stir in milk. Cook, stirring constantly, until a candy thermometer reads 248° (firm-ball stage). Remove from heat and stir in vanilla. Pour into prepared pan (do not scrape saucepan). Cool completely before cutting.