01 - Preheat oven to 375°F. Lightly grease a mini muffin tin or line with paper liners.
02 - In a large bowl, whisk together all-purpose flour, granulated sugar, baking powder, baking soda, salt, ground cinnamon, and ground nutmeg until well blended.
03 - In a separate bowl, whisk pumpkin purée, eggs, whole milk, melted butter, and vanilla extract until thoroughly combined.
04 - Add wet mixture to dry ingredients and stir gently until just incorporated. Avoid overmixing for the best texture.
05 - Fold in shredded cheddar cheese, grated Parmesan cheese, and chopped chives (if using) until evenly distributed throughout the batter.
06 - Spoon batter into prepared muffin cups, filling each about three-quarters full for optimal rise.
07 - Place tin in oven and bake for 18–20 minutes, or until muffin balls are golden and a toothpick inserted into the center pulls out clean.
08 - Allow muffin balls to cool in the tin for 5 minutes, then transfer to a wire rack. Serve warm.