Preheat the oven to 350 F. Line a 12 cup muffin pan with paper liners. In a large bowl, whisk together flour, sugar, cocoa powder, salt, and baking soda. Add in the eggs, melted butter and vanilla extract, and mix until smooth.
Fold in the butterscotch baking chips. Evenly divide the batter between the paper cups. Bake for 15-20 minutes.