Preheat oven to 425 degrees. Line a standard 12-count muffin pan with cupcake papers then set aside.
Soak old fashioned oats and whole milk in a mixing bowl for 30 minutes.
In a separate bowl whisk together butter, honey, egg and vanilla until combined. Set aside.
In a separate bowl, sift together flour, cinnamon, baking powder, baking soda and salt. Set aside.
After oats have soaked for half an hour, add them to the wet ingredients and stir with a wooden spoon until incorporated.
Add dry ingredient to wet ingredients and stir with a wooden spoon until just combined. Do not overmix.
Gently fold 1 cup of blackberries to the batter. Reserve remaining blackberries for the topping in the next step.
Distribute batter evenly among 12 muffin liners then top with remaining blackberries and a sprinkling of rolled oats.
Bake for 5 minutes at 425 degrees. Keeping the oven door closed, reduce temperature to 350 degrees then bake for 15 additional minutes or until a toothpick inserted into the center of a muffin comes out clean. Avoid overbaking.
Remove muffins from the oven and cool in the muffin pan for 5 minutes. After 5 minutes, remove muffins from the pan and place on a wire rack to cool to room temperature.
Muffins will keep in an airtight container at room temperature up to 2 days.
