Preheat oven to 350 degrees. Line cupcake pan with paper liners.
In a large bowl, cream together the butter and sugar until light and fluff.
Add in the vegetable oil and one egg at a time. As soon as each one is incorporated, add another. Once all the eggs are combined, beat for an additional 2 minutes. It will become thick and very pale.
Measure out the buttermilk and add the vanilla extract to it. Set aside.
In a separate bowl, sift together the cake flour, baking powder, baking soda, and salt. Stir to incorporate.
Alternately add the flour and milk mixture, starting and ending with flour. Mix on medium speed until combined.
Fill the cupcake liners about two-thirds full. Place into the preheated oven and bake for 17 minutes. Test the centers of the cupcakes with a toothpick to make sure they're done. Moist crumbs are okay, batter is not.
Remove from the oven and let cool completely.
In a large bowl, add in the butter and cream cheese. Beat until smooth.
Add in the dry jello mix, powdered sugar, and milk. Beat until incorporated. If it's too thick add an additional tablespoon of milk. For a fluffier frosting, beat on high for 30 seconds to 1 minute.
Add the frosting into a piping bag fit with a 1M tip.