Place your butter into the Instant Pot Bowl, and then press the saute' button. Let it melt. Just keep on moving it around, so it doesn't burn (it only takes a minute or so)
Then add the marshmallows, saute', until the marshmallows are completely melted and the mixture is well blended, stirring constantly.
Then remove the entire pan from the Instant Pot, please use Instant Pot gloves and place it on a hot pad, so it doesn't burn your surface.
Mix in the cereal, mix well. So everything is well blended. Meanwhile, spray your lasagna pan with non-stick cooking spray.
Spread your batter into the prepared pan and smooth with a spoon.
Let set and then cut into squares.