Healthy blueberry and walnut muffins

(according to my family and Karel, these are the BEST muffins I have EVER made)
Makes 18 muffins

Wet ingredients:
1 egg
1 apple (peeled, then shredded)
1 tsp vanilla extract
1 cup milk
1 tbsp honey
1-3 tbsp water (at the end)

Dry ingredients:
2 tsp cinnamon
2 tsp baking powder
1 cup whole wheat flour
1/4 cup oats
1 cup blueberries (fresh, washed)
2 tbsp chopped walnuts
2 tbsp chopped dark chocolate (or shaved)

1. Preheat oven to 350 degrees.
2. Mix together dry ingredients (except blueberries). Stir until combined.
3. Mix together wet ingredients (except water). Stir well.
4. Pour wet ingredients into dry bowl and mix. Add blueberries.
5. Add additional water until batter is easy to mix (consistency should look a little lighter than pancake batter).
6. Pour a heaping TBSP of batter until muffin tin (about 3/4 full).
*optional: top with a sprinkle of cinnamon sugar
7. Bake for 30-40 min or until top of muffin is golden brown.