Line an 8-inch x 8-inch square pan with parchment paper. Coat with non-stick cooking spray. set aside.
Add the sweetened condensed milk and white chocolate to a large microwave-safe bowl. Microwave for 1 minute and then stir the mixture together. If the chocolate hasn’t fully melted, microwave it for an additional 30 seconds and stir. Repeat as needed. Once the chocolate is melted, stir in the vanilla extract.
Transfer the fudge to the prepared pan and spread it out evenly using the back of a spoon or an offset spatula. Decorate the top of the fudge with sprinkles while the fudge is still soft. (This way the sprinkles will stick once it sets up.)
Place the fudge in the fridge to chill for at least 4 hours or up to overnight.
Remove the fudge from the fridge and cut it into small squares. (I usually cut a 5x5 grid to get 25 pieces.) Serve slightly chilled.
Notes
This is a very soft fudge. If you want a fudge that is a little firmer (and sturdier), use 5 cups of white chocolate chips instead of the recommended 4 cups.
Store any leftover fudge in an airtight container in the fridge for up to 1 month or freeze fro up to 3 months (individually wrapped in waxed paper).
You can swap in different themed sprinkles to match any occasion - holidays, birthdays, bridal showers, etc.