Preheat oven to 425 degrees Line a 15-by-10-inch jelly-roll pan with heavy duty aluminum foil. Spray foil with nonstick cooking spray.
Arrange saltines in an even layer on prepared pan.
In a medium saucepan, bring butter and brown sugar to a boil over medium-high heat. Cook for 2 minutes. Remove from heat, and stir in condensed milk. Pour mixture over crackers.
Bake for 10 minutes. Sprinkle with chopped white chocolate. Let stand for 1 to 2 minutes to soften. Using a small offset spatula, spread softened chocolate evenly over baked toffee. Sprinkle with pecans and cranberries. Let cool completely.
Break toffee into cracker size pieces. Store in an airtight container for up to 5 days.