Preheat and prep: Heat oven to 375°F (190°C).
Line a 12-cup muffin tin with paper liners or grease lightly.
Whisk dry ingredients: In a large bowl, whisk flour, baking powder, baking soda, salt, cinnamon, nutmeg, ginger, and cloves until well combined.
Mix wet ingredients: In a separate bowl, whisk brown sugar and eggs until smooth. Add pumpkin puree, oil, milk, and vanilla. Whisk until just blended.
Combine: Pour wet ingredients into the dry.
Stir with a spatula until the flour disappears. Do not overmix. Fold in any mix-ins.
Fill the cups: Divide batter evenly among the 12 cups, filling about 3/4 full. Sprinkle tops with coarse sugar or cinnamon-sugar if using.
Bake: Bake 17–20 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Cool: Let muffins rest in the pan for 5 minutes, then transfer to a rack to cool.
Enjoy warm or at room temperature.