Preheat your oven to 350°F (175°C). In a medium saucepan over low heat, combine the butter and bittersweet chocolate chips. Stir occasionally until melted and smooth. Remove from heat and let it cool slightly.
In a large mixing bowl, add the granulated sugar, salt, and vanilla extract to the melted chocolate mixture. Whisk together until well combined. Then, add in the eggs, one at a time, mixing well after each addition.
In another bowl, whisk together the all-purpose flour and baking soda. Gradually add this dry mixture into the wet ingredients, stirring until just combined.
Gently fold in the chopped Butterfinger candy bars, ensuring they are evenly distributed throughout the cookie dough.
Line your baking sheet with parchment paper. Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart. Bake in the preheated oven for 10-12 minutes or until the edges are set but the centers are still soft.
Remove the cookies from the oven and let them cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely. Enjoy these decadent treats warm or at room temperature!
