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. In a medium bowl, whisk together flour, salt, and baking soda. In a large bowl, combine butter and sugar and mix until it is fluffy.
Add in egg and vanilla extract and mix until smooth. Add in the flour mixture, and mix until it is fully combined. Fold in the crushed Oreo cookies and chopped chocolate bars.
Evenly divide the brownie batter between the lined muffin pans. Top each one with the cookie dough. Bake for 20-25 minutes.
