In a small bowl, combine the oats with 1/2 cup of the milk. Let the mixture sit for 10 minutes.

In another bowl, combine the raisins with 1/4 cup of the milk. Let them sit while the oats are sitting.

Preheat the oven to 350ºF. Line 12 muffin cups with paper liners or spray with nonstick cooking spray.

In a large bowl, combine the egg and the brown sugar, mixing until smooth.

Melt the butter slightly - it should be part liquid and part solid. You can do this in the microwave or on the stove.

Add in the butter, along with the vanilla, to the sugar mixture. Stir together. The mixture may have a few lumps, but should be mostly smooth.

Add in the all-purpose flour, whole wheat flour, baking soda, cinnamon, and salt. Add the remaining milk and stir to combine.

Add the soaked oats and raisins, along with any milk in the bowls, to the mixture. Fold together until combined.

Divide the mixture evenly between the prepared muffin cups. Sprinkle a little bit of turbinado sugar on top of each muffin.

Bake in the preheated oven until a tester inserted in the center comes out with only a few moist crumbs, about 16-18 minutes.

Let the muffins cool slightly before removing from the tin.