Preheat your oven to 350°F. Prepare a 13x9-inch cake pan by either greasing it with non-stick spray or lining it with parchment paper. Set aside.
In the bowl of a stand mixer, combine the cake mix, water, oil, and eggs. Mix thoroughly, scraping down the sides of the bowl as needed to ensure everything is well incorporated.
Pour the batter into the prepared cake pan and bake for 30-35 minutes, or until the center is fully set. Remove from the oven and allow the cake to cool completely.
For the frosting: Using a stand mixer, combine half of the powdered sugar, softened butter, vanilla, and salt. Mix on low speed until blended, scraping down the sides of the bowl as needed.
Add the remaining powdered sugar along with the milk. Mix on low speed until combined, then increase to medium speed and beat for about one minute, or until the frosting is light, fluffy, and smooth.
For the cake balls: Once the cake has cooled, crumble it into small pieces and transfer to the bowl of a stand mixer.
Add approximately 1 cup of frosting to the crumbled cake and mix using the paddle attachment on low speed until the mixture comes together. If the mixture is too dry and doesn’t hold its shape when pressed, add more frosting as needed.
Scoop out small portions of the mixture using a tablespoon or a small ice cream scoop, then roll them into neat balls with your hands.
Arrange the cake balls on a parchment-lined baking sheet. Once finished, place the sheet in the refrigerator or freezer for 15-30 minutes, or until the balls are firm.
For the coating: While the cake balls chill, melt the white chocolate or candy melts. Place them in a microwave-safe bowl and heat in 30-second intervals, stirring after each interval, until fully melted and smooth.
Remove the chilled cake balls from the fridge or freezer. Using a spoon, dip each ball into the melted white chocolate, ensuring it is fully coated.
Gently tap off the excess chocolate on the side of the bowl, then place the coated ball back onto the parchment-lined sheet.
Immediately top each coated ball with St. Patrick’s-themed sprinkles, as the white chocolate sets quickly—especially on chilled dough.