Grease a square pan (8x8 or 9x9 inch) and set aside.
Spread the cake mix on a microwave-safe plate and spread to an even layer.
1/2 cup cake mix (white, yellow or funfetti)
Microwave on high for 30 seconds; stir and repeat until it's been microwaved a total of 90 seconds. (To be extra safe, scoop the cake mix to a mound in the middle of the plate and take its temperature; you want it to be 160℉ or higher. If it's not, continue to microwave in 30 second increments). Let the cake mix cool.
In a large microwaveable bowl, add the butter and marshmallows.
10 ounces marshmallows, 1/3 cup butter
Cook on high for 3 minutes, stirring every 30 seconds, or until the butter and marshmallows are melted.
Add the vanilla and cake mix; stir well.
1 teaspoon vanilla extract
Stir in the cereal and sprinkles.
4 1/2 cups Rice Krispies cereal, 1/4 cup sprinkles (I recommend using sequins or jimmies)
Pour into the prepared pan then using a greased rubber spatula, press the mixture into the pan.
Melt the white chocolate and drizzle over the Rice Krispie treats; top with more sprinkles if desired.
2 ounces white chocolate chips or almond bark
Let cool, cut into bars and enjoy!