Preheat oven to 375 F. Line 12 muffin cups with liners, or spray with baking spray.
In a large bowl, combine flour, brown sugar, baking powder, spices, baking soda, and salt. Add carrots and walnuts, stir to combine.
In a separate bowl, combine pineapple, milk, butter, eggs, and vanilla.
Add wet ingredient mixture to the bowl of dry ingredients, stir gently to combine - batter should be lumpy.
Spoon batter into muffin cups, filling each about ⅓ full.
Divide the filling between the muffin tins, aiming for a general tablespoon of filling in the center of each - leaving room around it.
Finally, divide the remaining batter between the muffin cups, allowing the batter to fully encase the filling.
Bake in a 375 degree F oven for 22 to 25 minutes or until golden and a wooden toothpick inserted in centers comes out clean. (Note: Only insert it about ⅓ of the way down. If you hit cream cheese, it’ll be wet no matter how done it is!)
Cool in muffin cups on a wire rack for 5 minutes, before serving