Heat oven to 350 degrees.Grease bottom and sides of 13x9-inch pan with shortening or cooking spray.
In large bowl, beat sugar,butter,vanilla and egg with an electric mixer on medium speed; or mix with a wooden spoon until light and fluffy. Stir in graham cracker crumbs,four and salt. Reserve 2 cups of graham cracker mixture; press remaining into the pan for the crust.
Sprinkle chocolate chips over the crust; and press slightly. Drop marshmallow creme or mini marshmallows over chocolate chips.Sprinkle with the remaining graham cracker mixture; pressing lightly.
Sprinkle more mini marshmallow's over the top. Bake 17-22 minutes or until marshmallow's are puffed and light golden brown. Cool at least 30 minutes. When cool; cut into bars. Serve and enjoy!!