In a large mixing bowl, cream together the softened unsalted butter, granulated sugar, and light brown sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

Fold in the pumpkin puree until well combined.

In a separate bowl, whisk together the flour, cocoa powder, baking powder, baking soda, salt, ground cinnamon, nutmeg, and cloves.

Gradually add the dry ingredient mixture to the wet batter, stirring gently until just combined.

Fold in the chocolate chips and chopped nuts if using.

Preheat the oven to 350°F (175°C) and prepare the baking pan.

Pour the batter into the prepared pan and spread it evenly.

Bake for 25 to 30 minutes until a toothpick inserted comes out with a few moist crumbs.

Allow to cool in the pan for at least 15 minutes before transferring to a wire rack to cool completely.