Melt the Marshmallow Mixture: In a large pot over medium-low heat, melt butter. Add mini marshmallows, stirring continuously until smooth. Remove from heat and stir in vanilla extract.
Mix with Cereal: Gently fold in Rice Krispies cereal, making sure it's evenly coated.
Shape the Easter Eggs: Lightly grease your hands with cooking spray. Scoop small handfuls of the mixture and shape into egg forms. Place on a parchment-lined baking sheet to cool.
Decorate (Optional): Drizzle with melted white chocolate and sprinkle with Easter-themed sprinkles. Let set for about 15 minutes before serving.
