Process crackers in a food processor until fine; transfer to a mixing bowl. Pulverize pretzels, grinding until almost fine (some small pieces should remain). Add pretzels to crumbs and mix with butter and 2 Tbs. sugar.
Sprinkle the mixture evenly into the prepared pan, using a measuring cup to â€œtampâ€ down the crust. Bake for 15-18 minutes, or until golden around the edges.
Whisk 1 cup sugar and flour together in a mixing bowl while crust bakes. Add condensed milk and eggs; whisk just until blended. Stir in lime juice and zest.
Pour filling over hot crust and bake 20 minutes or until filling is set and no longer jiggly in the center. Cool bars completely, then cover and chill until firm, at least 4 hours.
Heat cream in a saucepan until bubbles form around the edge. Off heat, add chocolate, whisk until smooth, then chill until cold. Just before serving, whip cream to soft peaks. Cut cold bars into squares and transfer to a platter.
Garnish each bar with a rosette of whipped cream or dollop some on each bar. Finish with a slice of lime.