Preheat oven to 350°F. Prepare two 8x8-inch baking pans with butter and flour.

In a medium bowl, sift together flour, cocoa powder, baking powder, baking soda, and salt.

In a small bowl, combine buttermilk and pumpkin puree, whisking until smooth.

In a mixer, beat butter, sugars, and vanilla until fluffy. Add eggs one at a time.

Alternate adding the flour mixture and buttermilk mixture to the batter, starting and ending with the flour.

Divide batter evenly into prepared pans and bake for 18-26 minutes, until a toothpick comes out clean.

Prepare whipped cream: Whip heavy cream until soft peaks form. Fold in confectioners' sugar and pumpkin mixture.

Make ganache: Bring heavy cream to a boil, pour over chocolate chips, and stir until smooth.