Add the mini marshmallows and butter to a microwave-safe bowl.
Melt the marshmallows and butter together in the microwave, heating in 30-second bursts and stirring between each until smooth and bubbly, about 1-2 minutes. The mixture should be glossy and fragrant.
Stir in the vanilla extract into the melted mixture, combining until fragrant. This adds a warm aroma and enhances flavor.
Pour the Rice Krispies cereal into the bowl with the melted marshmallow mixture.
Gently fold the cereal into the marshmallow mixture with a spatula, ensuring all the cereal is evenly coated and sticky. Be careful not to crush the cereal too much.
Transfer the mixture into a parchment-lined dish, then press it down firmly with the back of the spatula or your fingers to create an even layer. Don’t pack it too tight; just press firmly enough to hold together.
Let the mixture sit at room temperature for about 15-20 minutes to set. For quicker setting, refrigerate for 10 minutes, but avoid freezing to prevent it from becoming too hard.
Once set, lift the block out of the dish using the parchment edges. Use a sharp knife to cut into 12-16 squares, pressing down firmly and slicing cleanly. Wipe the knife clean between cuts for neat pieces.
Optional: Drizzle melted chocolate over the bites or add sprinkles before they fully set for a decorative touch. Let the chocolate firm at room temperature or in the fridge for about 5-10 minutes.
Arrange the bites on a plate and serve immediately, or store in an airtight container at room temperature for up to 3 days or in the fridge for a week. Enjoy the crispy, gooey texture with every bite!
