In a large bowl combine rolled oats and milk. Mix together well and let stand for 20 minutes. The oats will become very soft.
Preheat oven to 400°F/200°C. Grease a 12 cup muffin tin or line with paper cups. You can also use a jumbo 6 cup muffin tin. Add egg, brown sugar, vegetable oil, melted butter, molasses and vanilla to the softened oats. Mix well until smooth.
In a small bowl whisk together all purpose flour, baking powder, baking soda, cinnamon and salt. Add gradually to the oat mixture and stir just until all traces of dry flour have disappeared. Do not over mix.
Divide batter evenly among prepared muffins cups. If desired, sprinkle some rolled oats on top of each one for added texture and taste. Bake 18-22 minutes (25-28 minutes for 6 large muffins). A toothpick inserted in the center should come out clean.
Cool muffins in pan for 5-7 minutes before transferring onto wire racks. Serve warm with butter.