Line a 7-8 inch square baking dish with aluminum foil or parchment paper. Set aside.
Set a medium saucepan over medium heat. Add sweetened condensed milk, butter, white chocolate chips and stir until smooth.
Add white cake mix and vanilla extract. Whisk slowly for a minute or two until it starts to bubble, and then remove from heat.
Stir in half of the sprinkles, and spread the mixture evenly into the prepared pan.
While still warm, add remaining sprinkles across the top and press them lightly into the surface.
Refrigerate for 2 hours to firm up.
Using a rigid spatula, loosen the fudge from the edge of the pan, cut pieces and lift out for serving. Enjoy!
