Preheat your oven to 350°F (175°C). Grease the muffin tin or line it with muffin liners.
In a large mixing bowl, whisk together the flour, sugar, baking powder, salt, and cinnamon until well combined.
In another bowl, mix the milk, melted butter, eggs, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix; it’s okay if the batter is slightly lumpy.
Gently fold in the shredded carrots, raisins, chopped walnuts, and chocolate chips, if using.
Evenly distribute the batter into the prepared muffin tin, filling each cup about two-thirds full.
Bake in the preheated oven for 18-20 minutes or until a toothpick inserted in the center comes out clean.
Remove from the oven and let the muffins cool in the tin for 5 minutes before transferring them to a cooling rack.
For a festive touch, consider adding a light drizzle of cream cheese icing after they have cooled.