Preheat oven to 350°F and line a muffin tin with paper liners.
In a large bowl, whisk together flour, baking powder, baking soda, cinnamon and all spice.
In a separate bowl, mix grated carrots, walnuts, and raisins, brown sugar, granulated sugar, vegetable oil, eggs, and vanilla extract.
Pour wet ingredients into dry ingredients and mix until just combined.
Divide batter evenly among muffin cups, filling each about ¾ full.
Bake in preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Allow muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving. Sprinkle them with chopped walnuts or drizzle with maple syrup.