Grease a standard 12-cup muffin tin with nonstick spray.
In a large bowl, whisk together the 1 cup pumpkin puree, ¼ cup plain whole milk yogurt, ¼ cup unsalted butter, and 1 large egg.
Stir in the 1 ¼ cups oat flour, ¾ cup sugar, 1 teaspoon cinnamon, ½ teaspoon ginger, ½ teaspoon nutmeg, 1 teaspoon baking powder, ½ teaspoon baking soda, and ¼ teaspoon fine salt. Add the 1 cup regular or mini semisweet chocolate chips if using.
Portion into the prepared muffin tin using about a heaping 1 tablespoon per mini cup. Preheat the oven to 375℉, and rest the batter while the oven heats. Bake for about minutes, until a cake tester inserted into the center comes out clean.
Cool the muffins in the pan for about 5 minutes, then turn them out onto a rack to cool completely.
Notes
Swap all-purpose gluten-free flour - If you wish, you can use 2 ¼ cups of your favorite 1:1 gluten-free flour blend or my homemade gluten free flour blend for the oat flour (although they won't be oat flour muffins!).
For the oat flour - If you can't do oat flour, substitute sorghum flour.
To make dairy-free - Use dairy-free yogurt and non-dairy butter or melted coconut oil for the unsalted butter.
To make refined sugar-free - Swap in ½ cup of pure maple syrup for the brown sugar.
Butternut squash or sweet potatoes - Use a can of butternut squash puree (or make it yourself) in these muffins for a slightly different flavor! You can also make these into sweet potato muffins by using 1 cup of mashed sweet potatoes for the pumpkin puree.