• Preheat the oven to 350° F. Line the 9x13 inch baking dish with aluminum foil or parchment paper. Leave enough overhang on both sides. So that its easy to remove bars when they have cooled. Set aside.
• Crush the graham crackers in a food processor or in a big ziploc bag. In a medium bowl, mix Graham cracker crumbs with sugar and melted butter to make a crust. Press graham cracker mixture into the lined baking dish and bake for 7 minutes. Remove from oven and let it cool.
• In a large bowl using handheld or stand mixer fitted with a paddle attachment, cream the butter, granulated sugar and brown sugar together on medium to high speed. Beat for about 2 minutes until smooth and combined. Add vanilla extract and eggs. Scrape the sides of the bowl down as needed. Beat well until light and creamy. Stir in flour, salt and baking soda just until combined. Then mix in the chocolate chips and 2 cups of the marshmallows by hand.
• Spread the cookie dough over the graham cracker crust by dropping spoonfuls of batter evenly around the dish. Gently press it together. Make sure not to disturb the graham cracker crust beneath.
• Bake for about 18 minutes at 350° F. Then remove from the oven, top with remaining 1 cup marshmallows and pieces of Hershey milk chocolate bars. Return to oven to finish baking. Bake about 10 minutes more, until golden brown on top. The center should be mostly set but little gooey. Trust me that's how you would wanna eat.
• Remove from oven and allow to cool completely. Cut into bar size. Enjoy!

Notes

• Sprinkle handful chocolate chips on the bars as soon as you remove from the oven. Let it melt slightly. The Bars don't need these extra chocolate chips but by doing so, it makes extra gooey. I highly recommend it.