Preheat your oven to 325 degrees F. Spray an 8×8 square inch cake pan with cooking spray, line with parchment paper, and spray again. Set aside.
In a medium sized bowl, whisk together the flour, baking soda, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, oil, and sugar on high until fluffy and smooth, about 4 minutes.
With the mixer on medium speed, start adding the egg whites, one at a time, to the bowl, scraping the bottom and the sides of the bowl between each addition. After all the eggs have been added, beat on medium speed for 1 minute. Add the sour cream and vanilla. Beat on medium speed for 30 seconds.
Turn the mixer on low and add half of the flour mixture and half of the buttermilk to the butter mixture and mix until fully incorporated. Finally, add the rest of the flour mixture and the rest of the buttermilk, while mixing on low. With a rubber spatula, fold in the sprinkles.
Add the the batter to the prepped pan, and carefully smooth the batter with a small offset spatula and bake until a toothpick comes out clean, or with only a few crumbs on it, about 25-30 minutes. Depending on your oven.
Let the cake completely cool, once the cake has cooled, place the cooked cake into a medium size bowl, add the cream and vanilla extract. Mix until the mixture becomes moist and can hold its shape.
Using a small cookie scoop, scoop and roll in the palm of your hands into small balls. Place in the fridge while you make the crumb coating on the outside.
For the outside crumb
Preheat the oven to 325°F and line a baking sheet with parchment paper. Set aside
In a medium size bowl, combine the sugar, flour, baking powder, and salt use a fork to combine. Once combined, add the melted butter and vanilla extract. Stir together until the mixture starts to come together and looks gritty. It should resemble crushed graham cracker. Add the sprinkles and stir to combine. Make sure there are no large clumps. You want a friend crumb.
Transfer the mixture out onto your prepped baking sheet into a and bake for 7 minutes, take the pan out of the oven and with a fork, gently mix around the crumb mixture. Bake for 5 more minutes. Let the mixture completely cool before assembling.
When everything is ready to assembly, melt the white chocolate over a double broiler and once completed melted, add the vegetable oil.
Make sure the chocolate mixture is slightly warm before dipping your cake balls into it.
Using a toothpick or a skewer, dip the cake ball in the melted white chocolate, use the edge of the bowl to wipe off the excess chocolate, you want the thinnest coat of white chocolate.
Once the chocolate has been wiped off, roll the cake ball onto the sprinkled crumb. Remove it from the skewer and gently roll it together in the palm of your hands to make it a perfect ball.
Repeat the process for all cake balls, then place them on a parchment-lined tray to set.
Allow the cake balls to set up for 30 minutes in the fridge before serving!