Preheat the oven to 350°F (175°C) and line a 12-cup muffin tin with paper liners. Rookie mistake alert: don’t skip this step.
Mix dry ingredients in a bowl: flour, baking soda, baking powder, salt, cinnamon, nutmeg, and ginger. Whisk it all together so no clumps remain.
Combine wet ingredients in another bowl: oil, brown sugar, eggs, vanilla, and pumpkin puree. Whisk until smooth.
Fold dry into wet: Gently stir until just combined. Don’t overmix, or your muffins will be tough.
Add mix-ins: Chocolate chips and walnuts go in last, folded carefully.
Fill muffin cups about ¾ full. Don’t overstuff, or you’ll have muffin volcanoes.
Bake for 20–25 minutes, or until a toothpick comes out clean. The house will smell like fall—try not to eat them all at once.
Cool for 10 minutes in the pan, then transfer to a wire rack. Patience is a virtue… kinda.