Grease twelve 2 1/2-inch muffin cups or line with paper bake cups; set aside.
In medium mixing bowl stir together flour, baking powder, pumpkin pie spice, baking soda and salt. Make will in center of dry mixture. In another medium mixing bowl combine egg, buttermilk, brown sugar and oil. Add egg mixture and carrots all at once to dry mixture. Stir just until moistened (batter should be lumpy).
Spoon batter into prepared muffin cups, filling each 2/3 full. In small mixing bowl combine walnuts or pecans or granulated sugar. Sprinkle over batter. Bake in 400° oven 15 to 20 minutes or until golden. Cool in muffin cups on wire rack 5 minutes. Then remove muffins from muffin cups. Serve warm. Makes twelve.