Creating these Double Chocolate Pumpkin Muffins is simple if you follow these steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or grease it lightly.
2. Mix Dry Ingredients: In a large bowl, sift together the all-purpose flour, whole wheat flour, cocoa powder, baking powder, baking soda, salt, cinnamon, and nutmeg.
3. Combine Sugars: In another bowl, whisk together the granulated sugar, brown sugar, and eggs until well combined.
4. Add Pumpkin: Stir in the pumpkin puree, vegetable oil, and vanilla extract to the egg mixture until smooth.
5. Combine Mixtures: Gradually add the dry mixture to the wet mixture, stirring gently until just combined. Be careful not to overmix.
6. Fold in Chocolate Chips: Gently fold in the semi-sweet chocolate chips and chopped nuts if using.
7. Fill Muffin Tin: Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.
8. Bake: Place in the preheated oven and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
9. Cool: Remove from the oven and let the muffins cool in the tin for about 10 minutes before transferring them to a wire rack to cool completely.

These steps will guide you in creating moist and delectable muffins that everyone will love.