Streusel Topping

1. In a small bowl, stir together the crushed Oreos, flour, sugar, butter, and salt until you have large, sandy clusters.
2. Set aside while you prepare the muffin batter.

Muffin Batter

1. Heat & Prep: Preheat your oven to 425°F (220°C). Line a standard 12-cup muffin tin with paper liners.
2. Dry Ingredients: In a large bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt.
3. Wet Ingredients: In another bowl, beat the eggs with sugar until smooth. Stir in the oil, sour cream, milk, and vanilla until the mixture looks uniform.
4. Combine: Gently fold the dry ingredients into the wet mix just until no streaks of flour remain. Overmixing can make muffins tough.
5. Add Oreos: Fold in the chopped Oreo cookies so they’re evenly distributed throughout the batter.
6. Fill Muffin Cups: Spoon the batter into liners, filling each about three-quarters full.
7. Top with Streusel: Generously sprinkle the Oreo streusel over each muffin, pressing lightly so it adheres.
8. Bake: Bake at 425°F (220°C) for 5 minutes, then reduce the heat to 350°F (180°C) and continue baking another 18–20 minutes, or until a toothpick inserted in the center comes out clean and the tops spring back when pressed.
9. Cool: Let muffins rest in the pan for 5 minutes, then transfer to a rack to cool completely.