1. Preheat the oven to 400 degrees F.
2. In a bowl, add and combine together the all purpose flour with sugar, baking powder and salt. Mix well and make a well in the center.
3. In another bowl, add and combine bran with milk. Stir in the egg, vegetable oil, peanut butter and mix well.
4. Stir in another cup of milk and mix until well combined.
5. Transfer the wet ingredients into the bowl of flour and mix until well incorporated.
6. Take a greased 12 cup muffin pan and add the batter evenly into each cup. Bake this in the preheated oven for 20 - 25 minutes or until golden brown. Once done, set aside to cool.
7. Serve these muffins with warm milk or coffee.