Butter an 8-inch square baking pan. Line with enough wax paper to overhang 2 sides by 2 inches.
In pot, combine chips and milk over medium heat cook, stirring constantly, until mixture is melted and smooth. Remove from heat; stir in vanilla extract. Cool 1 minute.
Stir in candy bars. Spread mixture evenly in pan. Refrigerate until firm, at least 2 hours. Use wax paper to help remove from pan. Peel off paper, then cut into squares.
