In a large saucepan, melt the butterscotch chips, peanut butter, and unsalted butter over low heat, stirring constantly until smooth.

Remove the saucepan from heat and let the mixture cool slightly, about 5 minutes.

Gently fold in the mini marshmallows and crispy rice cereal, ensuring everything is well coated.

Press the mixture into a greased 9×9-inch baking pan, using a spatula to smooth the top.

Refrigerate for at least 1 hour, or until set.

Cut into squares and serve.

For a nut-free version, substitute the peanut butter with sunflower seed butter. You can also add a handful of chopped nuts or dried fruit for extra texture and flavor. If you prefer a chocolate twist, try using chocolate chips instead of butterscotch chips, or drizzle melted chocolate over the top before refrigerating. To make the squares more festive, consider adding colorful sprinkles or edible glitter on top before they set.