Preheat oven to 400ยบ Grease or paper-line 10 to 12 muffin cups.
Combine cereal, buttermilk, egg and oil in a bowl. Let stand for 10 minutes, stir to break up cereal. Combine flour, sugar, baking powder and cinnamon in separate bowl.
Add cereal mixture all at once to flour mixture, stirring just until combined. (Batter will be thick) Fold in raisins.
Divide batter between 10 to 12 muffin cups.
Make crunchy topping
Combine crushed bran flakes, brown sugar and melted butter.
Divide evenly among muffin cups.
Bake 20 to 25 minutes or until toothpick inserted in center comes out clean.