• Preheat the oven to 350℉ and line a standard muffin tin with cupcake liners.
• Combine the cake mix, water, vegetable oil, butter flavored extract, and egg whites in a large bowl.
• Mix with a hand or stand mixer on medium speed until well incorporated, about 1 to 2 minutes.
• Fold in ¾ cup of the crushed Butterfinger bits.
• Divide the batter evenly among the muffin cups, filling each about two-thirds full.
• Sprinkle the remaining ¼ cup crushed Butterfinger bits over the tops of the cupcakes.
• Bake for 18 to 20 minutes, until a toothpick inserted in the center comes out clean.
• Cool the cupcakes completely on a wire rack before frosting.

Frosting

• Cream the butter and cream cheese together with a mixer until light and fluffy, about 2 minutes.
• Mix in the vanilla extract.
• Add the powdered sugar 1 cup at a time, alternating with a tablespoon of heavy whipping cream, until fully incorporated.
• Continue mixing for 1 minute, until the frosting turns light and creamy.
• Fold in the ⅓ cup crushed Butterfinger bits.
• Pipe the frosting onto the cooled cupcakes.
• Top each cupcake with the remaining 2 tablespoons crushed Butterfinger bits.