Line a 9x13-inch baking dish with parchment paper and lightly grease it.
In a large saucepan over low heat, melt the white chocolate chips and butter, stirring constantly.
Once melted and smooth, remove from heat and stir in vanilla extract and salt.
Let the mixture cool slightly, then gently fold in the marshmallows until fully coated.
Add most of the sprinkles and candies, reserving a few for topping.
Transfer the mixture to the prepared pan and press it down gently with a spatula.
Sprinkle remaining decorations on top and gently press them in.
Chill in the refrigerator for 1 hour or until set.
Cut into squares and serve.