Lightly grease a 9x13-inch baking pan with butter.
Place Oreos in a zip-top bag and crush with a rolling pin until you have small pieces (not powder). If you want, sift out the finest crumbs through a strainer to keep the treats from turning gray.
In a large pot over medium-low heat, melt the 6 tablespoons of butter. Add 10 oz (about 5 cups) of the mini marshmallows and stir often until completely melted.
Remove from heat, stir in vanilla, then add the cereal and mix until well coated.
Quickly fold in the remaining marshmallows and the crushed Oreos – just until combined.
Pour the mixture into the prepared pan. Use a greased spatula to gently spread it evenly. Don’t press down hard or the treats will become tough.
Let cool completely at room temperature, then cut into 20 squares and pack into lunchboxes!
Notes
Nutrition per serving: Calories: 162, Total Carbs: 29g, Net Carbs: 28.6g, Fats: 5g, Protein: 1g.