Preheat oven to 350℉.
Butter two loaf pans.
In a medium bowl, whisk together flour, pumpkin pie spice, salt, baking powder, baking soda, and sugar.
In a large bowl, whisk together the starter, and melted butter or coconut oil. Then stir in the pumpkin puree, eggs, buttermilk, and vanilla.
Add the flour mixture to the pumpkin mixture a little at a time, beating after each addition.
While that is beating, heat the baking chocolate in a medium saucepan over medium heat, just until melted. Remove from heat.
Whisk it up to get any lumps out, add the cocoa powder to the melted chocolate and whisk again.
Transfer about half of the pumpkin mixture to the chocolate and mix that up really well.
Now transfer the chocolate batter back to the bowl with the pumpkin batter and swirl it together gently.
Add the batter to the prepared pans and smooth the top.
You could also just add each one separately to the prepared pans and swirl it then.
Bake in a preheated oven for 45-55 minutes.
Check for doneness by sticking a toothpick or cake tester into the center. If it comes out clean, it’s done.
Remove from pans and cool on a wire rack.
Let cool for at least 20 minutes before cutting for the best texture.