01 -  Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners. 
 02 -  In a medium bowl, whisk flour, baking soda, baking powder, cinnamon, nutmeg, ginger, and salt until evenly combined. 
 03 -  In a large bowl, beat together granulated sugar, brown sugar, root beer, vegetable oil, eggs, pumpkin purée, and vanilla extract until smooth. 
 04 -  Gradually fold the dry ingredients into the wet mixture until just combined, being careful not to overmix. 
 05 -  Divide batter evenly among the cupcake liners, filling each approximately two-thirds full. 
 06 -  Bake for 20 to 22 minutes, or until a toothpick inserted in the center of a cupcake comes out clean. 
 07 -  Allow cupcakes to cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely. 
 08 -  Beat cream cheese and butter together until creamy. Gradually blend in powdered sugar, then mix in vanilla and 1 tablespoon root beer. If needed, add more root beer for preferred consistency and flavor. 
 09 -  Frost cooled cupcakes using a piping bag or spatula. Optionally garnish with root beer candies or a sprinkle of cinnamon.