Preheat oven to 350°F (175°C) and grease or line a muffin tin with paper liners.
In a large mixing bowl, combine mashed banana, date syrup, oil, milk, egg, and vanilla extract. Mix until smooth and well incorporated.
In a separate bowl, whisk together flour, baking powder, and cinnamon.
Gradually fold the dry ingredients into the wet ingredients, stirring until just combined. Do not overmix, as this can result in dense muffins.
Gently fold in the chocolate chips and nuts if using.
Spoon batter into muffin cups, filling each to about ¾ full.
Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Let cool in the tin for 5 minutes before transferring to a wire rack to cool completely.
Enjoy warm or store in an airtight container for up to 3 days at room temperature. For longer storage, freeze and reheat as needed.