White-chocolate and sprinkle-covered rice krispies treats
Line a 9 x 9 pan with parchment paper (or foil) with an overhang and lightly spray with cooking spray. Set aside.
In a large pot, add the butter and place over medium heat. Melt, stirring occasionally. As soon as the butter is melted, add 8 cups of the miniature marshmallows. Stir constantly until the marshmallows are JUST melted.
Remove from the heat and stir in the salt, vanilla extract, rice krispies cereal, and the rest of the marshmallows (2 and 1/2 cups)
Mix until all the ingredients are well incorporated and then press the mixture gently into the prepared pan. Lightly spritz your hands with cooking spray and then gently press down the krispies treats. Don't press them too hard as you'll get a denser krispie treat.
Set the krispies aside and add the white chocolate and vegetable oil to a microwave safe bowl. Microwave in bursts of 15 seconds stirring in between each burst for 10 seconds until the chocolate is melted and smooth.
Using a spoon drizzle the melted white chocolate over the bars (or you can transfer the chocolate to a plastic bag, cut off the tip, and drizzle evenly over the bars).
Immediately add the sprinkles and allow the bars to set up at room temperature.
These bars are best enjoyed the same day.