In a large bowl, combine graham cracker crumbs, condensed milk, melted butter, and vanilla extract until blended.
Line a 9×9-inch pan with parchment paper and firmly press the mixture into an even layer.
Microwave white chocolate chips in 30-second intervals, stirring between each, until smooth.
Spread melted chocolate evenly over the crust, then sprinkle marshmallows, festive sprinkles, and pecans.
Refrigerate for at least 2 hours, or until firm.
Cut into squares and serve chilled.
