Preheat the oven to 375°F. Line a muffin pan with 12 paper liners.
In a medium bowl, combine the flour, baking powder, baking soda, cinnamon, ginger, nutmeg and salt and whisk together.
In another large bowl, combine the sugar, oil, eggs, vanilla, and milk and whisk well.
Add the dry ingredients to the wet ingredients. Stir together until just combined, making sure to scrape the sides and bottom of the bowl. Fold the carrots, walnuts, and raisins into the batter.
Divide the batter among the paper liners (they will be almost full). Sprinkle the tops with more sugar, if you like.
Bake for 18 to 22 minutes, or until the tops are springy and a toothpick comes out with a few crumbs. Let cool for 5 minutes in the pan, then transfer to a cooling rack to cool completely.
Notes
Accurately measure the flour. Using too much flour will cause the carrot muffins to be dry. The best way to measure flour is to weigh it on a food scale. If you don't have one, fluff and spoon the flour into the measuring cup, then level it off with a knife.
Use freshly grated nutmeg. I typically buy pre-ground cinnamon and ginger, but I always freshly grate nutmeg when adding it to baked goods for the most vibrant flavor. Nutmeg loses its flavor relatively fast once ground, so jarred ground nutmeg has far less strength than fresh!
Don't over-mix the batter. Over-mixing the batter can lead to tough and dense muffins because the gluten in the flour will over-develop. Mix the wet and dry ingredients until just combined, and then gently fold in the carrots, walnuts, and raisins. Do not use a mixer.
Don't overfill the muffin cups. Leave room for the muffin batter to rise; otherwise, the muffin tops will spread and stick to the pan or overly brown the edges.
Add a crunchy sugar topping. These muffins are extra delicious topped with sugar for a crunchy, sweet muffin top. Sprinkle with sanding sugar or coarse turbinado sugar for a sparkling finish!