01 -  Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or grease thoroughly. 
 02 -  In a large bowl, whisk together flour, baking powder, baking soda, salt, ginger, cinnamon, nutmeg, cloves, and optional cayenne pepper until evenly blended. 
 03 -  In a medium bowl, whisk pumpkin purée, maple syrup, buttermilk (or whole milk with lemon juice), melted butter, egg, and vanilla until smooth. 
 04 -  Pour wet ingredients into dry ingredients. Add crystallized ginger. Fold gently with a spatula until just combined; avoid overmixing. 
 05 -  Divide batter evenly among muffin cups, filling each almost to the top. 
 06 -  If desired, drizzle each muffin with a touch of maple syrup and sprinkle with chopped nuts before baking. 
 07 -  Bake for 20 to 22 minutes, until a toothpick inserted in the center comes out clean. 
 08 -  Cool muffins in the tin for 5 minutes, then transfer to a wire rack to cool completely.