Preheat oven to 400°F

Put the Graham cracker crumbs in a large mixing bowl; set aside.

Cook corn syrup and brown sugar in a saucepan over medium heat for 4-5 minutes, until mixture comes to a boil just around the edges, stirring occasionally. Remove from heat; stir in butter, baking soda and vanilla.

Pour syrup over mixture and stir to coat completely. Transfer to a greased 13x9-inch pan; press firmly to level. Place chocolate bars in a single layer over mixture; sprinkle with marshmallows.

Bake in preheated oven for 5-8 minutes, or until marshmallows are puffed and lightly golden browned. Remove from oven and top with mini chocolate chips.

Refrigerate for 1 hour until firm; cut into squares. Store in tightly covered container for up to 2 days.