Preheat oven to 350 degrees F. Line a 9x13 pan with parchment paper.
Combine melted butter with graham cracker crumbs and sweetened condensed milk and press down into pan.
Top with the M&M'S and bake for 20 minutes or until golden brown.
Melt white chocolate and drizzle over bars, top with extra M&M'S and let cool.
Cut into squares and enjoy!