In a medium bowl, stir together the flour, sugar, baking powder, baking soda and salt.
In a large bowl, combine the milk, oil, orange zest, orange juice and vanilla.
Pour half of the dry ingredients into the wet ingredients and stir until just combined, then repeat with the remaining dry ingredients.
Stir in the chocolate chips.*
Pour the batter into the paper-lined wells of a muffin tin.
Bake at 350 degrees for 18 to 20 minutes until lightly golden and a toothpick inserted into the center of a muffin comes out clean.
When the muffins are cool, dip their tops in a glaze if desired. To make the glaze, simply stir together one cup of confectioners' sugar and two tablespoons of orange juice. Adjust the ingredients as needed to create a thicker or thinner consistency.
*The regular sized chocolate chips I used sunk to the bottom of this fairly thin batter. To alleviate most of this issue, I suggest tossing the chocolate chips in flour before adding them to the batter or using mini chocolate chips.
Recipe by Love & Flour at http://www.loveandflour.com/monday-muffins-orange-chocolate/