01 - Preheat oven to 350°F. Line a standard 12-cup muffin tin with paper liners or lightly grease each cavity.
02 - In a large mixing bowl, whisk together the pumpkin puree, mashed banana, eggs, vegetable oil, milk, and vanilla extract until the mixture is smooth.
03 - In a separate bowl, combine the all-purpose flour, granulated sugar, brown sugar, baking soda, baking powder, salt, cinnamon, nutmeg, and ginger. Stir thoroughly to distribute leaveners and spices evenly.
04 - Add the dry ingredient mixture to the wet mixture. Gently stir until just combined, ensuring not to overmix the batter.
05 - If desired, gently fold in the chopped walnuts or pecans and chocolate chips.
06 - Divide batter evenly into the prepared muffin cups, filling each approximately three-quarters full.
07 - Place the muffin tin in the oven and bake for 20 to 22 minutes, or until a toothpick inserted in the center comes out clean.
08 - Allow muffins to cool in the pan for 5 minutes, then transfer to a wire cooling rack to cool completely before serving.