Melt butter in a large pot over low heat. Add marshmallows and stir until melted and smooth.

Remove from heat and fold in cereal until coated.

Press mixture into a greased or lined 9x13 pan in an even layer. Let cool at room temperature for 1 hour.

Cut into squares or shapes with a cookie cutter.

Melt candy melts in separate microwave-safe bowls. Transfer to piping bags for drizzling, or use for dipping.

Drizzle back and forth over the treats, or dip each one partially or fully. Add sprinkles immediately.

Place on parchment or wax paper and let set completely. Store in an airtight container for up to 3 days.