Preheat the oven to 375°F and line your muffin pan(s) with paper liners.
Whisk the flour (with xanthan gum), brown sugar, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger in a medium-sized bowl.
Whisk the egg, oil, milk, and pumpkin puree in another bowl.
Add wet ingredients to the dry ingredients and mix with a whisk until well combined.
Fold in the chocolate pieces with a spatula.
Fill the prepared muffin pans about 2/3 full and bake for about 22-24 minutes or until a toothpick inserted in the center of a muffin comes out clean. The muffin should bounce back when gently pressed with your fingertip; that's when you know it's done.
Cool the muffins in the pan before enjoying them. Store leftover muffins in an airtight container at room temperature for 3-5 days or up to a month in the freezer.
Notes
About the Flour: I used Bob’s Red Mill 1-to-1 Gluten-Free Flour, which includes xanthan gum. If using another gluten-free flour blend that doesn't contain xanthan gum, add one teaspoon of it.Spices: You can use two teaspoons of pumpkin pie spice instead of cinnamon, ginger, and nutmeg.Dairy-Free: To make this recipe dairy-free, use a dairy-free milk alternative and dairy-free chocolate chips. I suggest Enjoy Life chocolate chips.Vegan Alternative: To make the muffins vegan, use the dairy-free substitutes listed above and an egg replacer. I recommend Bob’s Red Mill Egg Replacer prepared with three tablespoons of water instead of the two the directions instruct. You can also use a flax egg by mixing one tablespoon of flax meal with three tablespoons of warm water. After mixing, let the flax-water mixture sit for five minutes. It'll turn into a gel and can be added to your recipe.A Word About Pumpkin Puree: Be sure to use 100% canned pumpkin puree, not pumpkin pie mix or filling. Pumpkin pie mix or filling may contain gluten and yield vastly different results.