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 eggs, melted butter, and vanilla extract, and whisk until smooth. Fold in the crushed pretzels. Evenly divide the brownie batter between the prepared muffin cups. Bake for 20-25 minutes.