Preheat the oven to 350°F and line a cupcake pan with St. Patrick’s Day cupcake liners.
In a large bowl combine the cake mix, egg whites, milk, sour cream, melted butter, vegetable oil, vanilla extract, and mint extract. Mix until smooth and fully combined.
Add green gel food coloring and mix until the batter reaches a bright festive green.
Fill the cupcake liners about two-thirds full. Bake for 16 to 18 minutes, or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool completely.
To make the frosting, beat the softened butter until smooth. Gradually add powdered sugar, then mix in the vanilla and heavy cream. Beat until light and fluffy.
Stir the crushed Mint Oreos into the frosting until evenly combined.
Pipe the frosting onto the cooled cupcakes. Finish with green sprinkles and St. Patrick’s Day royal icing decorations. Insert decorative straws or themed toppers for a fun finishing touch.