Heat oven to 350°F. In food processor, place 3 cups of the pretzels and 1/4 cup brown sugar. Cover; process until finely chopped. Stir in melted butter. Press mixture in bottom and up sides of ungreased 9-inch glass pie plate.
In medium microwavable bowl, microwave 3/4 cup butter and the chocolate chips uncovered on High 1 to 2 minutes, stirring once, until melted and smooth. Stir in 3/4 cup brown sugar and the granulated sugar. Stir in eggs. Stir in whipping cream, flour and vanilla. Pour into crust-lined plate.
Bake 50 minutes or until center is set. Cool completely, about 3 hours.
Coarsely crush remaining 1/2 cup pretzels. Top each slice of pie with dollop of whipped topping. Drizzle with caramel topping; sprinkle evenly with crushed pretzels.