White Chocolate S’mores Gooey Cake Bars

• 1 box yellow cake mix
• 1 large egg
• 1 stick (1/2 cup) unsalted butter, softened
• 4 1/2 full graham crackers
• 10 ounce bag white chocolate chips
• 2 cups mini marshmallows
• 1/2 cup sweetened condensed milk

Instructions
See full instructions on : picky-palate.com