In a small saucepan on medium heat, add your Magical Butter, sweetened condensed milk, and white chocolate chips. Stir until smooth and clump free.
Add the white cake mix and vanilla extract. Whisk slowly for a minute or two until it starts to bubble, then remove from heat.
Gently fold in half of the sprinkles, this way the colors do not run.
Pour the mixture into your silicone trays. TIP: transfer it to a measuring cup first for an easier pour.
Top with the remaining sprinkles then set in the fridge for 2 hours to firm up.