1. Preheat your oven to 180°C (350°F) and line a mini muffin tray with paper liners.
2. In a large mixing bowl, add the whole grain flour.
3. Gradually add water to the flour, mixing until you achieve a smooth batter consistency.
4. Wash the blackberries thoroughly and cut them into small pieces suitable for a baby.
5. Gently fold the blackberry pieces into the batter.
6. Spoon the batter evenly into the mini muffin tray.
7. Bake in the preheated oven for about 20 minutes or until the muffins are lightly golden and cooked through.
8. Allow the muffins to cool completely before serving to your baby.

Summary:
This recipe is good for babies as it provides essential nutrients from whole grains and blackberries. The whole grain flour is rich in fiber and essential minerals, while blackberries provide vitamins and antioxidants. It is easy to hold, soft to chew, and perfect for baby-led weaning.

Storing Options:
Store the cooled muffins in an airtight container in the refrigerator for up to 3 days, or freeze for up to 1 month.

Possible Side Effects/Allergies:
Always check for possible allergic reactions, especially to grains or berries. Introduce new foods one at a time and consult with your pediatrician if unsure.