Line an 8x11-inch baking dish with parchment paper.

Put white chocolate chips and shortening in a microwave-safe bowl. Microwave for 1 minutes and then give it a good stir. Microwave in 30 second increments, stirring after each one, until completely melted.

Add marshmallows and stir to coat all the marshmallows. Work quickly or the marshmallows will start to melt!

Pour the marshmallows into your prepared pan and use a rubber spatula to extend the marshmallows to all sides. Sprinkles on any sprinkles you want to use.

Refrigerate until completely set, at least a couple hours. Cut into squares and bring to room temperature before serving.