Line a 9x9 baking dish with parchment paper and lightly spray with pam cooking spray
Using a medium sauce pan, combine the sweetened condensed milk, butter, white chocolate chips over medium heat.
Gradually stir until mixture is melted
Once melted, remove from heat and mix in the cake mix and vanilla until combined
Fold in 1/4 C of the sprinkles
Scoop the fudge out of the pot and into the baking dish and top with remaining sprinkles
Place the baking dish in the fridge over night before cutting into 1 inch squares.