Line a 9x13-inch baking pan with foil and spray with baking spray. Set aside.

Add the butter to a medium sized pot and melt on the stove top over medium-high heat. Remove one cup of mini marshmallows from the bag and set aside. Once the butter has melted, add the bag of mini marshmallows to the butter. Once the marshmallows start to melt, add a pinch of salt to the pot. Continue to stir the mixture continuously until all the marshmallows have melted. Once the marshmallows are completely melted, remove the pot from the stove top.

Immediately stir in the vanilla extract to the marshmallow mixture. Add the Rice Krispies cereal one cup at a time to the marshmallow mixture, stirring each cup of cereal in completely before adding the next. Continue adding cereal to the marshmallow mixture, until all the cereal is mixed in the marshmallow mixture. Stir in the cup of mini marshmallows that you had set aside and then gently fold in the Oreo cookie pieces and semi-sweet chocolate chips.

Pour mixture into prepared pan and GENTLY press mixture evenly into the pan. Spray one of your hands with baking spray to gently press the mixture into the pan, if the mixture keeps sticking to your hand or fingers. Option to sprinkle additional chocolate chips on top. Let treats cool completely before cutting into desired sized squares.