Line a 9x13" pan with foil; grease with 2 tsp. butter; spread pretels on the bottom of pan; (kinda flatten to make a single layer) sprinkle pecans on top of pretzels.
In a large heavy saucepan; combine brown sugar, cubed butter, corn syrup milk and salt; cook and stir over medium heat until candy thermometer reads 240* soft ball stage; remove from heat; stir in vanilla; pour over pretzel mixture.
In a microwave safe bowl, melt chocolate chips and 1 tblspn. shortening; stir until smooth. Spread over the caramel layer. In another bowl microwave vanilla chips and 1 tsp. shortening, and stir until smooth; drizzle this in lines across the chocolate layer... let cool; then lift foil out of pan and cut into bite sized pieces.. should make 70... Enjoy!