In mixing bowl, mix 1 cup margarine, sugar and salt with a mixer until combined. Stir in flourPress on the bottom of an ungreased jelly roll pan in a 375* oven for 10-15 minutes or until very lightly brownIn a saucepan, mix together condensed milk and margarine over medium/low heat until starts to bubble. Stirring continuouslyCook for 3 minutes more (and stir!). Remove from heat and stir in vanillaBake for 10-15 minutes or until lightly brownRemove from oven and immediately spread scatter chocolate chips on top of warm bars. Let sit for 2 minutes and spread carefully with a spatula, creating a frostingSprinkle with crushed pretzelsChill in fridge for 1 hour. Cut into squares and serve.