In a large saucepan, melt the butter over low heat. Once melted, add the mini marshmallows and marshmallow fluff. Stir continuously until everything is melted and smooth. Remove the pan from heat and stir in the vanilla extract. Gently fold in the puffed rice cereal, mixing until the cereal is fully coated. Let it cool for 2 to 3 minutes until warm but safe to handle.

Lightly grease your hands with butter or cooking spray. Roll the mixture into bite-sized balls, about 1 to 1.5 inches in diameter. If the mixture is crumbly, press gently to shape each ball. Place the shaped balls on a parchment-lined baking sheet and let them cool completely.

In a microwave-safe bowl, melt the white chocolate chips or candy melts in 20–30 second intervals, stirring between each round until smooth. If the chocolate is thick, stir in 1 tablespoon of coconut oil to loosen the texture. Let the melted chocolate sit for a minute or two so it slightly thickens for easier coating.

Dip each rice krispie ball into the melted white chocolate until fully coated. Use a fork to lift and gently tap off excess chocolate. Return the coated balls to the parchment-lined tray and immediately sprinkle with red, green, and white nonpareils before the chocolate sets.

Allow the coated rice krispie balls to set at room temperature, or place the tray in the refrigerator for 15 to 20 minutes to speed up the process. Once the chocolate is firm, transfer the balls to a serving dish or airtight container. Stack neatly to show off the festive colors.