Prepare your baking dish by greasing it lightly with butter or lining it with parchment paper.

In a large pot over low heat, melt the butter and mini marshmallows together while stirring continuously.

Once melted and smooth, remove the pot from heat and stir in the vanilla extract, followed by the white chocolate chips until smooth and creamy.

Fold in the rice cereal gently, ensuring it is well coated with the marshmallow mixture.

If using sprinkles, set aside a handful before pouring the mixture into the prepared baking dish, and then sprinkle them on top of the mixture once it’s in the dish.

Use a spatula or your hands (greased with butter) to press the mixture evenly into the baking dish.

Let the treats cool at room temperature, then cut into squares or rectangles to serve.