1. Preheat the oven to 375°F (190°C). Butter non-stick miniature muffin pans or line them with paper liners.
2. In a large bowl, combine all-purpose and whole wheat flour, baking powder, baking soda, and salt. In another bowl, combine sugar and cocoa; gradually whisk in milk until blended. Whisk in egg, orange zest, orange juice, and butter. Pour over dry ingredients and sprinkle with chocolate chips; stir just until moistened.
3. Spoon the batter into the prepared muffin pan filling 24 deep or 36 shallow cups. Bake, in batches as necessary, for about 15 minutes or until the tops are firm to the touch. Cool in pan for five minutes and then transfer to rack to cool completely.
Recipe and photo are provided by Dairy Farmers of Canada. For more recipe ideas, visit dairygoodness.ca.