In a large deep pot, heat the butter on medium heat, just until melted. Set aside 2 full cups of mini mallows. Add the remainder of the marshmallows into the pot with the melted butter, continue to heat the butter and marshmallows stirring until melted smooth. Remove the butter marshmallow mixture from heat. Measure out 9 cups of cereal and place in a large mixing bowl. Pour butter marshmallow mixture into cereal and gently start to fold together. When about half way combined, add the 2 cups of mini marshmallows that were set aside, and continue to folding until well combined. Oil a 9x13 baking dish lightly, and then pour cereal mixture into baking dish. Add oil to hands and then press the cereal evenly in baking dish. Let cool and set for about 45-60 minutes before cutting bars. Keep in airtight container for 2-3 days.