1. Prepare your baking pan by greasing it with cooking spray or butter.
2. In a large mixing bowl, combine the salted butter and creamy peanut butter until smooth and creamy.
3. Gently fold in the Corn Flakes or Rice Krispies cereal until all the cereal is coated.
4. Add the regular marshmallows to the mixture and stir gently to combine.
5. Transfer the mixture into your prepared baking pan and press it firmly into an even layer.
6. Spread the mini marshmallows over the top and toast them using a kitchen torch or under the broiler until golden brown.
7. Melt the semi-sweet or dark chocolate in a double boiler or microwave-safe bowl until smooth.
8. Pour the melted chocolate over the toasted marshmallows and spread evenly.
9. Sprinkle with flaky sea salt if using, while the chocolate is still warm.
10. Let the bars cool at room temperature for about 30 minutes before cutting into squares.