Line a 9x9" baking dish with parchment paper and spray lightly with nonstick spray. Set aside.
Set a large heatproof bowl, over a pan of steaming water. In the bowl, combine the white chocolate chips, sweetened condensed milk, sugar cookie mix, butter, and vanilla. Heat over medium heat until melted, stirring frequently. The consistency will be thick like sugar cookie dough.
Once melted, remove the bowl from the heat and pour in half of the sprinkles. Set aside the remaining sprinkles for later. Working quickly, stir the sprinkles into the fudge base. Note-Some sprinkles will streak and melt, but that's ok.
Transfer the fudge mixture to the prepared baking dish. Smooth the top and gently press the remaining sprinkles onto the top of the fudge. Place the pan in the fridge for at least 2 hours for the fudge to set.
When the fudge has hardened, remove it from the baking dish and cut it into 25 equal-sized pieces.
Melt the white chocolate bark in a microwave-safe dish until runny and smooth. Use a spoon, a piping bag, or a squeeze bottle, to drizzle the fudge with the white chocolate. Let the chocolate harden and enjoy.