Preheat the oven to 400°F (200°C). Line a 12-cup muffin pan with paper liners, or lightly grease with oil.
In a large bowl, whisk together the plant milk, maple syrup, molasses (if using), oil, applesauce, vinegar, and vanilla until smooth.
Add the flour, wheat bran, brown sugar, baking powder, baking soda, salt, cinnamon, and nutmeg to the wet ingredients. Gently fold until just combined — the batter will be thick but moist.
Let the batter rest for 5 minutes to allow the bran to hydrate.
Divide the batter evenly among the muffin cups, filling nearly to the top. Sprinkle oats over each muffin, if desired.
Bake for 18–22 minutes, or until the tops are domed and spring back when lightly pressed.
Cool in the pan for 10 minutes, then transfer to a wire rack.
Slice in half while still warm and top with a square of butter, allowing it to melt before serving.